Research and Technology - NASA · Ames’ research and technology activities, and the stimulating challenges ahead. The accomplishments cited illustrate the contributions that Ames

Research and TechnologyN A S A A m e s R e s e a r c h

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Research and Technology

Ames Research Center

National Aeronautics and Space Administration

Ames Research CenterMoffett Field, California

NASA TM-112195

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Foreword

The mission of NASA Ames Research Center is to research, develop, verify, and transfer advanced aeronautics,space, and related technologies; to advance and communicate scientific knowledge and understanding of theuniverse, the solar system, and the Earth; and to enable the development of space for human enterprise. Empha-sis is placed on information systems technologies for aeronautics and space applications; on aviation operationssystems; and on the discipline of astrobiology, the study of life in the universe encompassing the Earth, space,and life sciences.

This report highlights the challenging work accomplished during fiscal year 1996 by Ames research scientists,engineers, and technologists. It discusses research and technologies that enable the Information Age, thatexpand the frontiers of knowledge for aeronautics and space, and that help to maintain U. S. leadership inaeronautics and space research and technology development. The accomplishments span the range of goals ofNASA’s four Strategic Enterprises: Aeronautics and Space Transportation Technology, Space Science, HumanExploration and Development of Space, and Mission to Planet Earth.

The primary purpose of this report is to communicate information—to inform our stakeholders, customers, andpartners, and the people of the United States about the scope and diversity of Ames’ mission, the nature ofAmes’ research and technology activities, and the stimulating challenges ahead. The accomplishments citedillustrate the contributions that Ames is making to improve the quality of life for our citizens and the economicposition of the United States in the world marketplace.

For further information on Ames research and technology projects, please contact the person designatedas the point of contact at the end of each article. An electronic version of this report is available atURL http//jit.arc.nasa.gov/atrs/index.html.

Henry McDonaldDirector

http://atrs.arc.nasa.gov/

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Aeronautics Enterprise

Overview ................................................................................................................................................. 1

Global Civil Aviation/Safety

Aviation Performance Measuring System.................................................................................................. 3Irving C. Statler

Aviation Safety Reporting System ............................................................................................................. 4Linda J. Connell

Crew Activity Tracking System ................................................................................................................. 5Todd J. Callantine

Study of Line Oriented Flight Training ...................................................................................................... 6Key R. Dismukes

Measuring Air Traffic Complexity ............................................................................................................. 7Irene V. Laudeman, Connie Brasil, Robert Branstrom

Operational Interventions to Human Error in Aircraft Maintenance .......................................................... 8Barbara G. Kanki, Vicki Dulchinos

Aircraft Separation Risk Model ................................................................................................................. 9Mary M. Connors

The Final Approach Spacing Tool ............................................................................................................ 11Tom Davis

Air/Ground Integration ............................................................................................................................. 11R. Slattery

The Traffic Management Advisor .............................................................................................................. 12Harry N. Swenson

Surface Movement Advisor ...................................................................................................................... 13Brian J. Glass

Simplified Vision Models for Display Quality Assessment ........................................................................ 14Al Ahumada

Perceptually Tuned Visual Simulation ...................................................................................................... 15Mary K. Kaiser

Entropy Masking in Visual Displays.......................................................................................................... 17Andrew B. Watson

Vertical Motion Simulator Advanced Simulator Network ......................................................................... 18William B. Cleveland

Intelligent Aircraft Control System ............................................................................................................ 19Charles C. Jorgensen

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Aeronautics Enterprise (continued)

Global Civil Aviation/Affordability

Facilitating User Route Preferences in En Route Airspace ......................................................................... 20Bob Vivona, Mark Ballin, Steve Green, Ralph Bach, Dave McNally

Conflict Probability Estimation for Free Flight ........................................................................................... 21Russell A. Paielli, Heinz Erzberger

Conflict Prediction Algorithms: Initial Field Test ....................................................................................... 23Dave McNally, Bob Vivona, Karl Bilimoria, Gerd Kanning, Steve Green, Ralph Bach,Allan McCrary, Ed Lewis

Assessing Controller Performance Under Simulated Free-Flight Conditions .............................................. 24Roger Remington, James Johnston, Eric Ruthruff, Maria Romera

Evaluating Cockpit Display of Traffic Information Displays and Route Assessment Toolsfor a Free Flight Environment ................................................................................................................... 25

Vernol Battiste, Walter W. Johnson

Cockpit Displays for Low-Visibility Taxiing .............................................................................................. 27David Foyle, Elizabeth M. Wenzel, Durand R. Begault

Multi-Sensor Image Registration ............................................................................................................... 29Misha Pavel, Al Ahumada, Barbara Sweet

Flow Visualization of a Full-Scale Rotor in Hover .................................................................................... 29Benton H. Lau, Alan J. Wadcock, Gloria K. Yamauchi

Skin-Friction Measurements on a Hovering Rotor ..................................................................................... 30Alan J. Wadcock, Gloria K. Yamauchi

Rotor Data Correlation ............................................................................................................................. 31Randall Peterson

Canard Rotor/Wing Hover Test ................................................................................................................ 32Stephen Swanson, John Madden

In-flight Dynamic Stall Research .............................................................................................................. 34Robert Kufeld, William Bousman

Stall Control of Helicopter Rotors ............................................................................................................. 34Khanh Q. Nguyen

Apache AH-64D Flight Test Predictions ................................................................................................... 35Earl P. N. Duque

Rotor-Wake/Fuselage Interaction.............................................................................................................. 36Paul M. Stremel

Navier-Stokes Simulation of High-Lift Aerodynamics ............................................................................... 37Karlin Roth, Stuart Rogers

Lift-Jet Effects on Powered-Lift STOVL Model ........................................................................................... 38Karlin Roth

Vortex Core Detection for Computational Grid Refinement ...................................................................... 38David Kenwright

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Global Civil Aviation/Affordability (continued)

Wingtip Vortex Flows............................................................................................................................... 39Jennifer Dacles-Mariani, Dochan Kwak

Transonic Overset Potential Solver ........................................................................................................... 40Terry Holst

Real-Time Particle Tracing in Time-Varying Flows ................................................................................... 41David Kenwright, David Kao

NASA Metacenter .................................................................................................................................... 42Mary Hultquist

Portable Batch System .............................................................................................................................. 43David Tweten

Developing a Cluster Computer from Workstations .................................................................................. 43Reese L. Sorenson

Planar Doppler Velocimetry Using Pulsed Lasers ..................................................................................... 44Robert L. McKenzie

Pressure-Sensitive Paint and Photogrammetry for Aeroelastic Experiments ............................................... 45Edward T. Schairer, Lawrence A. Hand

Visualizing Wind-Tunnel Experimental Data ............................................................................................ 47Samuel P. Uselton, Glenn Deardorff, Leslie Keely, Yinsyi Hung, Arsi Vaziri

Surface Tension Effects on Skin Friction Measurements ............................................................................ 48G. Zilliac, A. Celic

Fullerene Gear Design, Simulation, and Visualization .............................................................................. 49Albert Globus

Global Civil Aviation/Environmental Compatibility

Civil Tiltrotor Noise Abatement Approaches ............................................................................................ 51William A. Decker, Rickey C. Simmons

XV-15 Blade-Vortex Interaction Noise...................................................................................................... 52C. W. Acree, Megan S. McCluer, Cahit Kitaplioglu

Tiltrotor Aeroacoustic Model .................................................................................................................... 53Larry Young

Predicting and Analyzing Rotorcraft Noise ............................................................................................... 54Roger C. Strawn, Rupak Biswas, Lenny Oliker

Airframe Noise Measurements: Atmospheric Pressure .............................................................................. 55W. Clifton Horne, Julie A. Hayes, Michael E. Watts, Paul H. Bent

Airframe Noise Measurements: Pressures to 4.7 Atmospheres .................................................................. 56W. Clifton Horne, Stephen M. Jaeger, Mahendra Joshi, James R. Underbrink

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Revolutionary Technology Leaps/Innovative Technology and Tools

X-36 Pioneers Advanced Aerodynamics and Flight Controls .................................................................... 57Rodney Bailey, Mark Sumich

Closed-Loop Neural Control of Rotorcraft Vibration ................................................................................. 57Sesi Kottapalli

Coupled Navier–Stokes and Optimizer Analysis of a Transonic Wing ...................................................... 58Roxana M. Greenman, Samson Cheung, Eugene L. Tu

Parallel Unstructured Mesh Adaption ....................................................................................................... 59Rupak Biswas, Leonid Oliker, Roger Strawn

Load Balancing Adaptive Unstructured Meshes........................................................................................ 59Rupak Biswas, Leonid Oliker, Andrew Sohn

Initial Release of the Field Encapsulation Library ...................................................................................... 61Steve Bryson

RANS-MP: Portable Parallel Navier–Stokes Solver .................................................................................... 61R. Van der Wijngaart, Maurice Yarrow

Parallel Tools for Parallel and Distributed Computer Systems ................................................................... 63D. DiNucci, M. Frumkin, R. Hood, H. Jin, L. Lopez, R. Papasin, C. Schulbach, J. Yan

Numerical Aerodynamic Simulation Parallel Benchmarks 2.2 .................................................................. 65William Saphir, R. Van der Wijngaart, Alex Woo, Maurice Yarrow

Large-Scale Parallel Semiconductor Simulation ........................................................................................ 65Subhash Saini

Revolutionary Technology Leaps/Supersonic Technology

Nonlinear Aerodynamic Shape Optimization of High-Speed Research Configurations ............................. 66Susan Cliff, James Reuther, Ray Hicks

Surface Operations Behavioral Evaluation Interim Testbed for High-Speed Research ............................... 68Mary K. Kaiser

Revolutionary Technology Leaps/Access to Space

Propulsion Checkout and Control System................................................................................................. 69Ann Patterson-Hine

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Space Science Enterprise

Overview ................................................................................................................................................. 71

Progress in Exobiology

Remote Analysis of Martian Surface Materials .......................................................................................... 74D. Blake, P. Sarrazin, D. Bish, D. Vaniman, S. Chipera, S. A. Collins, T. Elliott

Stable Isotope Biogeochemistry of Hydrothermal Systems ........................................................................ 76David J. Des Marais

Fossilization Processes in Thermal Springs ............................................................................................... 77Jack Farmer, Sherry Cady, David J. Des Marais

Molecular Biomarkers for Stromatolite-Building Cyanobacteria ................................................................ 78Linda L. Jahnke, Roger E. Summons, Harold P. Klein

Earth-Threatening Comets Leave Tell-Tale Dust Trails .............................................................................. 80Peter Jenniskens, David Morrison

Capturing Cosmic Dust on Mir ................................................................................................................. 81Kenji Nishioka, Ted Bunch, Mark Fonda, Glenn Carle, Sherwood Chang, James Ryder, Janet Borg

Simple Peptides at Water-Membrane Interfaces ........................................................................................ 82Andrew Pohorille, Christophe Chipot

Silicon-Micromachined Gas Chromatography System .............................................................................. 84Thomas Shen, James Suminto, Frank Yang, Daniel Kojiro, Glenn Carle

Nitrogen Sources and Sinks on Early Earth ............................................................................................... 85David P. Summers

Progress in Planetary Systems

Planetary Rings ........................................................................................................................................ 86Jeff Cuzzi

Planetesimal Formation in the Protoplanetary Nebula .............................................................................. 87Jeff Cuzzi

PASCAL: A Mars Climate Network Mission .............................................................................................. 87Robert M. Haberle, David C. Catling, Steven C. Merrihew

The Center for Star Formation .................................................................................................................. 88D. Hollenbach, P. Cassen

Energetic Trapped Particles near Jupiter ................................................................................................... 89John D. Mihalov

Wavelet Software ..................................................................................................................................... 90Jeff Scargle

Time-Dependent Structures in Galaxies ................................................................................................... 90Bruce F. Smith, Richard A. Gerber, Richard H. Miller, Thomas Y. Steiman-Cameron

Galileo Encounters Jupiter: Results from the Probe ................................................................................... 91Richard E. Young

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Space Science Enterprise (continued)

Progress in Planetary Systems (continued)

Regolith Effects on Mars’ Climate ............................................................................................................. 92Aaron Zent

The Nature of the Martian Oxidants ......................................................................................................... 92Aaron Zent

A Thermo-Acoustic Oxidant Sensor ......................................................................................................... 93Aaron Zent

Progress in Astrophysics

Astrobiology in the Astrochemistry Laboratory ......................................................................................... 93Louis J. Allamandola, Scott Sandford, Max Bernstein, Robert Walker, Dave Deamer

Spectrum Synthesis of Hot Water in Sunspots and Selected Cool Stars ..................................................... 94Duane F. Carbon, David Goorvitch

A High-Altitude Site Survey for SOFIA...................................................................................................... 95Michael R. Haas, Leonhard Pfister

Kepler Mission Educational and Public Outreach Software ...................................................................... 96David Koch

Mid-Infrared Studies of Diffuse Interstellar Material .................................................................................. 97Thomas L. Roellig

Infrared Observations of G0.18-0.04 ........................................................................................................ 98Janet P. Simpson, Sean W. J. Colgan, Angela S. Cotera, Edwin F. Erickson, Michael R. Haas,Mark Morris, Robert H. Rubin

New 3.405-Micron Interstellar Emission from Organic Hydrocarbons ...................................................... 99Gregory C. Sloan, Jesse D. Bregman

Progress in Space Technologies

Assessment of the Cassini Command and Data Subsystem ....................................................................... 101Edward A. Addy

Automatic Telescope Project .................................................................................................................... 101John Bresina

Guide Star Tracker for Gravity Probe B Relativity Mission ........................................................................ 103John H. Goebel

Pulse-Tube Cryocooler Development ....................................................................................................... 103Peter Kittel

Automated Space System Experimental Testbed Project ........................................................................... 105Christopher Kitts

Amphion and Meta-Amphion................................................................................................................... 105Michael Lowry

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Space Science Enterprise (continued)

Progress in Space Technologies (continued)

Focal-Plane Sensor Array Development for Astronomy in Space .............................................................. 106Mark E. McKelvey, Robert E. McMurray, Jr., Craig R. McCreight

Intelligent Execution for Autonomous Spacecraft ...................................................................................... 108Barney Pell

New Millennium Program Deep Space 1 Flight Software Program Management ...................................... 108Scott Sawyer

Human Exploration and Development of Space Enterprise

Overview ................................................................................................................................................. 111

Astronaut Health/Science

Biochemical Markers of Bone Metabolism in a Rat Spaceflight Model ..................................................... 114Meena Navidi, Jeanne Wren, Sara Arnaud

Cerebrovascular Responses Prior to Fainting ............................................................................................ 115Kana Kuriyama, Toshiaki Ueno, Richard E. Ballard, Donald E. Watenpaugh,Suzanne M. Fortney, Alan R. Hargens

Chronic Exposure to Hyper-G Suppresses Otolith-Spinal Reflex in the Rat ............................................... 116Nancy G. Daunton, Merylee Corcoran, Robert A. Fox, Li-Chun Wu

“Dual Adaptation” to Space-Related Sensory Rearrangements .................................................................. 118Robert B. Welch

Technology Applications to Human Health

Virtual Environment Surgery Workbench ................................................................................................. 119Muriel D. Ross

Noninvasive Estimation of Pulsatile Intracranial Pressure Using Ultrasound ............................................. 120Toshiaki Ueno, Richard E. Ballard, John H. Cantrell, William T. Yost, Alan R. Hargens

MRI-Compatible Spinal Compression Harness ......................................................................................... 122Richard E. Ballard, Donald E. Watenpaugh, Iwane Mitsui, Klaus P. Fechner,Douglas S. Schwandt, Alan R. Hargens

Near-Infrared Spectroscopy to Monitor Forearm Muscle Oxygenation ..................................................... 123Gita Murthy, Alan R. Hargens

BIONA 1—Blood Flow Ion Analyzer........................................................................................................ 125John W. Hines, Christopher J. Somps

Intelligent Controller for Neurosurgery ..................................................................................................... 126Robert Mah

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Human Exploration and Development of Space Enterprise (continued)

Technology Applications to Human Health (continued)

Center for Health Applications of Aerospace Related Technologies (CHAART) ........................................ 128Byron Wood, Louisa Beck, Sheri Dister, Brad Lobitz

Telemedicine Spacebridge to Russia ........................................................................................................ 128Steve N. Kyramarios

Progress in Improving Space Travel

Advanced Life Support/Human Exploration and Development of Space Enterprise Activities ................... 129Dick Lamparter, Mark Kliss

Mir Hardware—Stepping Stone to Station ................................................................................................ 130Bonnie P. Dalton, James Connolly, Gary Jahns, Paul Savage

Wireless Network Experiment for Space Shuttle/Mir ................................................................................. 131Richard Alena

Engine Diagnostic Filter System................................................................................................................ 132Tarang Patel

Formal Lightweight Approaches to Validation of Requirements Specifications ......................................... 133Steve Easterbrook

Astronaut Health/Countermeasures

Autogenic-Feedback Training as a Potential Treatment for Postflight Orthostatic Intolerance ................... 135Patricia S. Cowings, William B. Toscano

Exercise for Long-Duration Spaceflight ..................................................................................................... 138Donald E. Watenpaugh, Richard E. Ballard, Karen J. Hutchinson, Jaqueline M. William,Andrew C. Ertl, Suzanne M. Fortney, Lakshi Putcha, Wanda L. Boda, Stuart M. C. Lee,Alan R. Hargens

Keiser SX-1 Variable Resistance Exercise Device ...................................................................................... 139Jennifer Pedley, Anthony Artino, Richard Ballard, Alan R. Hargens

Dehydration at Airline Cabin Altitude ...................................................................................................... 141John E. Greenleaf, Peter A. Farrell, Helmut Hinghofer-Szalkay

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Mission to Planet Earth Enterprise

Overview ................................................................................................................................................. 145

Ecosystem Science and Technology

AIRDAS—Use of Remote Sensing for Disaster Assessment and Management ........................................... 147James Brass, Vincent Ambrosia, Robert Slye

Bay Area Digital Georesource .................................................................................................................. 147Edwin Sheffner, Sheri Dister, Don Sullivan

Brazil/United States Environmental Monitoring and Global Change Program ........................................... 148James Brass, Vincent Ambrosia

Carnegie/Ames/Stanford Approach Model ................................................................................................ 149Christopher Potter

Digital Array Scanning Interferometer ...................................................................................................... 149Steve Dunagan, Philip Hammer

Effect of Landuse on Regional Estimates of Coniferous Forest Water and Carbon Budgets ........................ 151Joseph Coughlan, Jennifer Dungan

Landsat Program ...................................................................................................................................... 152Edwin Sheffner

Leaf Modeling .......................................................................................................................................... 152Lee F. Johnson, Chris Hlavka, Philip D. Hammer, David L. Peterson

Mapping Northern Ecosystems: Applications for Circumpolar Methane Exchange.................................... 153Vern Vanderbilt, Guillaume Perry, Joel Stearn

Modern Ecosystems Research: Effects of Increased UV-B Radiation.......................................................... 153Hector L. D’Antoni, J. W. Skiles

Optimizing an Ecosystem Model for Use on Parallel/Distributed Processors ............................................. 154J. W. Skiles, Cathy Schulbach

Paleoenvironmental Research .................................................................................................................. 155Hector L. D’Antoni

Scientists’ Intelligent Graphical Modeling Assistant .................................................................................. 155Jennifer Dungan

Atmospheric Chemistry

Airborne Natural Radionuclide Measurements in the Development and Validation ofGlobal Three-Dimensional Models .......................................................................................................... 156

Mark Kritz, Stefan Rosner, Robert Chatfield, Leonard Pfister

Reactive Nitrogen Data from the Upper Troposphere and Lower Stratosphere ......................................... 156Hanwant B. Singh, Alakh Thakur, Peter Mariani

Airborne Autotracking Sunphotometry ..................................................................................................... 157Philip B. Russell, John M. Livingston, James Hanratty, Damon Ried, Jill Bauman

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Mission to Planet Earth Enterprise (continued)

Atmospheric Chemistry (continued)

Analysis of Stratosphere/Troposphere Exchange ....................................................................................... 157Leonhard Pfister, Henry Selkirk

Use of Argus in Atmospheric Studies ........................................................................................................ 158Max Loewenstein

Airborne Tunable Laser Absorption Spectrometer ..................................................................................... 158Max Loewenstein, James R. Podolske

Convectively Generated Gravity Waves ................................................................................................... 159Leonhard Pfister

The ER-2 and DC-8 Meteorological Measurement Systems ...................................................................... 159K. Roland Chan, T. Paul Bui, Antonio A. Trias, Stuart W. Bowen, Jonathan Dean-Day

Environmental Research Aircraft and Sensor Technology ......................................................................... 160Steve Wegener

Global Emissions Inventories for Radon and the Cosmogenic Radionuclides ............................................ 161Mark Kritz

The Great African Plume: Tropical Carbon Monoxide and Ozone Simulation .......................................... 162Robert B. Chatfield

Instrument for Tropospheric Nitrogen Studies ........................................................................................... 163James R. Podolske

Reactive Nitrogen and Oxygenated Hydrocarbon Measurements during the PacificExploratory Mission.................................................................................................................................. 163

Hanwant B. Singh, W. Viezee, R. Chatfield, Y. Chen, D. Herlth, R. Kolye

Subsonic Aircraft: Contrail and Cloud Effects Special Study...................................................................... 163Owen B. Toon, Steve Hipskind, Duane Allen, Paul Bui, Roland Chan, Mike Craig, Guy Ferry,Steve Gaines, Warren Gore, Eric Jensen, Joe Jordan, Stefan Kinne, Bill McKie, Peter Pilewskie,Rudi Pueschel, Tony Strawa, Annette Walker

Stratospheric Tracers of Atmospheric Transport ........................................................................................ 164Stephen Hipskind, Michael Craig

Tropospheric Aerosol Radiative Forcing Observational Experiment .......................................................... 165Philip B. Russell, John M. Livingston, Wendy Whiting

Atmospheric Physics

Fine Particle Emissions by Aircraft ............................................................................................................ 166Rudolf F. Pueschel, Guy V. Ferry, Anthony W. Strawa, Duane Allen

FIRE Phase III ........................................................................................................................................... 166Peter Pilewskie, Warren Gore

Laboratory Spectroscopy of Carbon Dioxide in Support of Planetary Atmospheres Research .................... 167Lawrence P. Giver, Charles Chackerian, Jr.

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Mission to Planet Earth Enterprise (continued)

Atmospheric Physics (continued)

Near-Infrared Remote Sensing of Cloud Liquid Water .............................................................................. 167Peter Pilewskie, Warren Gore

Quantitative Infrared Spectroscopy of Minor Constituents of the Earth’s Atmosphere ............................... 168Charles Chackerian, Jr., Lawrence P. Giver

Stratospheric Transport ............................................................................................................................. 169Rudolf F. Pueschel, Guy V. Ferry, Anthony W. Strawa, Duane Allen

SUCCESS Irradiance Measurements ......................................................................................................... 170Peter Pilewskie, Warren Gore

Appendix

Color Plates (1–22) ................................................................................................................................... 172

Aeronautics and Space Transportation Technology Enterprise

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O v e r v i e wNASA’s mission for the Aeronau-

tics and Space Transportation Tech-nology (ASTT) Enterprise is to pioneerthe identification, verification,transfer, application, and commercial-ization of high-payoff aeronautics andspace transportation technologies.Ames’ researchers and technologistssupport this mission by seekingenabling revolutionary technologicaladvances that will provide air andspace travel for anyone, anytime,anywhere more safely and moreaffordably, and with less effect on theenvironment and with improvedbusiness opportunities and globalsecurity.

This pursuit of revolutionarytechnologies addresses bold, mid-term and long-term goals of theASTT Enterprise to enable dramaticimprovements in aviation and spacetransportation. This reflects nationalpriorities as outlined by the NationalScience and Technology Council.These goals are grouped into threeareas, or as they are called, threepillars: “Global Civil Aviation,”“Revolutionary Technology Leaps,”and “Access to Space.” The followingsections outline these goals andAmes’ FY96 accomplishments towardachieving them.

Pillar 1: Global Civil AviationToday, with over 11,000 air-

planes in commercial service world-wide, the United States faces stronginternational competition in this vitalarea whose products are the largestpositive industrial contributor to theU.S. balance of trade. Projects linkedto world economic growth suggestthat air travel demand will triple overthe next 20 years. Therefore, topreserve our Nation’s economichealth and the welfare of the travelingpublic, NASA must provide high-risktechnology advances that willcontribute to safer, more affordable,more environmentally compatible airtravel.

The highlighted FY96 accom-plishments address the followinggoals of the Global Civil Aviationpillar:1. Safety goal: Reduce the aircraft

accident rate by a factor of 5within 10␣ years, and by a factorof 10 within 20 years.

2. Affordability goals: (a) Whilemaintaining safety, triple theaviation system throughput, inall weather conditions, within10␣ years and (b) reduce the costof air travel by 25% within10␣ years, and by 50% within20␣ years.

3. Environmental compatibility goal:Reduce the perceived noise levelsof future aircraft by a factor of 2(from those of today’s subsonicaircraft) within 10␣ years, and by afactor of 4 within 20 years.

Research and developmentconducted by the ASTT Enterprise hasbeen structured to be led by specifiedNASA research centers according tothe primary roles and missions thathave been assigned to each center.Ames is the lead center for the HighPerformance Computing and Com-munications (HPCC) Program and forthe research and technology (R&T)base programs in aviation operationssystems, information technology, androtorcraft. In addition, Ames leads theEnterprise core competencies in theareas of human factors, air-trafficmanagement, information systemtechnologies, and rotorcraft R&T.

Ames’ significant involvementin the safety goal includes humanfactors, information technology, andcondition-based maintenance. Amesmade significant contributions towardaddressing this goal, contributionsthat led to advances in aviationperformance measuring, aviationsafety reporting, crew activity track-ing, air-traffic complexity, aircraft-separation risk modeling, air andground integration, and human errorin aircraft maintenance.

Airlines and businesses losebillions of dollars annually as a result

A E R O N A U T I C S A N D S P A C E T R A N S P O R T A T I O N

T E C H N O L O G Y E N T E R P R I S E

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of delays and lost productivity owingto weather and congestion in theairspace system. Under affordabilitygoal (a) (above), Ames’ major effortin research and development of air-traffic management automationconstitutes virtually all of NASA’swork in that area. Accomplishmentsinclude articles on controller perfor-mance under simulated free-flightconditions, techniques for low-visibility taxi and ground-collisionavoidance, and conflict-predictionalgorithms.

Reducing the costs of aircraftoperation and maintenance is a majorchallenge. NASA’s test facilities andcore expertise in materials, structures,aerodynamics, propulsion, analyticalmethods, and computational tools arekey elements in helping to revolution-ize aircraft design and manufacturing.NASA’s research efforts are focusedon innovative design techniques andstructural concepts. Ames’ contribu-tions to affordability goal (b) comefrom rotorcraft, national taskingfacilities, and research and develop-ment of computational tools. SeveralAmes projects contributed to rotor-craft research and technologyactivities, which include rotor aero-dynamics, testing of new concepts,stall control, in-flight dynamic stallresearch, and vortex flows. Examplesof accomplishments that enhancecomputational tools are vortex-coredetection and tracking of particles intime-varying flows. Improvements inthe use of facilities are highlighted inthe following pages by articles onplanar Doppler velocimetry, pressure-sensitive paint and photogrammetry,and visualization of experimentaldata. A high-risk, long-term researcheffort directed to the manufacture offullerene nanotechnology gears is alsodescribed.

For research related to theenvironmental compatibility goal,Ames has significant aeroacousticresearch and testing capabilities, themost recent advance in those capa-bilities being the Aeroacoustic

Modification Project at Ames’National Full-Scale AerodynamicsComplex (NFAC), which is currentlybeing completed. In this report,accomplishments related to helicopternoise and airframe noise arepresented.

Pillar 2: Revolutionary TechnologyLeaps

NASA’s charter is to explore high-risk technology areas that can revolu-tionize air travel and create newmarkets for U.S. industry. The tech-nology challenges for NASA includeaccelerating the application oftechnology advances, eliminatingthe barriers to affordable supersonictravel, and expanding generalaviation,

The highlighted FY96 accom-plishments address the following twogoals of the Revolutionary Technol-ogy Leaps pillar:1. Provide next-generation design

tools and experimental aircraft toincrease design confidence, andcut the aircraft developmentcycle time in half.

2. Reduce the travel time to the FarEast and Europe by 50% within20 years, and do so at today’ssubsonic ticket prices.

The next-generation design toolsand experimental aircraft goal willdramatically affect the way in whichbusiness is conducted. Its effect willbe felt across the three pillars, contrib-uting to every technology goal. Ameshas significant work in integrateddesign systems and the X-36 aircraft.Research is done at Ames in informa-tion technology to elevate the powerof computing tools through fuzzylogic, neural networks, and artificialintelligence. These tools will integratemultidisciplinary product develop-ment activities to dramatically cutdesign cycle times. Examples ofaccomplishments include neuralcontrol of rotorcraft vibration, cou-pling of flow-field computation toolswith design optimization tools, andparallel computational tools and

computations. Experimental aircraftare also invaluable tools for exploringnew ideas. An example is providedwith the use of advanced aero-dynamics and flight controls on theX-36 aircraft.

Under the high-speed transportgoal, Ames has diverse activities inwind-tunnel testing and simulation,external visibility, sonic boomminimization, and wing aerodynamicoptimization. Articles are presented inthis report to highlight these activities.

Pillar 3: Access to SpaceIn coming decades, NASA

envisions the space frontier as a busycrossroads of U.S.-led internationalscience, research, commerce, andexploration. Experience with this vastresource has already yielded newtreasures of scientific knowledge, life-enhancing applications for use onEarth, and fantastic celestial discover-ies. The potential for the future seemsalmost limitless.

Ames addresses the followinggoal of the third pillar, Access toSpace:1. Reduce the payload cost to

low-Earth orbit by an order ofmagnitude, from $10,000 to$1,000 per pound, within10␣ years.

As NASA’s lead center forthermal protection systems (TPSs)technology, Ames is charged withdeveloping new thermal protectionsystems that will enable vehiclesof the future to be built more eco-nomically and that will enableexisting ones to be upgraded atreduced cost. Ames maintains one ofthe world’s premier arc-jet complexesfor providing realistic simulations ofentry environments. These simulationsare essential for technology develop-ment, system validation, and systemqualifications. Ames supports the U.S.aerospace community in developingTPSs that will be necessary for thenation’s future space vehicles.



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GLOBAL CIVIL AVIATION/SAFETY

Aviation PerformanceMeasuring SystemIrving C. Statler

Flight Operations QualityAssurance (FOQA) programs usingflight-recorded data have beenproviding critical safety informationto non-U.S. airlines for over twodecades. Although the benefits ofthese programs have been demon-strated, the U.S. air carriers havefound them impractical to imple-ment because of the extensivelabor required to process the greatamounts of data that would typicallybe generated. A collaborative effortwas initiated in August 1993between the Federal AviationAdministration (FAA) and NASA toestablish and demonstrate thefeasibility of developing a set oftools that would allow very largequantities of flight data to be pro-

cessed automatically in order toaddress questions relating to opera-tional performance and safety.

The Aviation PerformanceMeasuring System (APMS) is provid-ing technical tools to facilitate thelarge-scale implementation of flight-data analyses at both the air-carrierand the national-airspace levels.APMS enhances the existingCommercial Off The Shelf (COTS)capabilities of FOQA, including thecapability of analyzing all the datacollected, in addition to merelyidentifying “exceedances” or“special events” (the figure showsthe APMS functions).

Phase 1 of the APMS effortended in December 1995. Phase 2focuses on three tasks: (1) selectionand implementation of an APMSclient-server database architecture;(2) development of a knowledge-based system for verifying anddiagnosing “special events” flaggedby COTS packages; and (3) construc-tion of a friendly user-interface in

Visual Basic. The client-serverdatabase architecture and methodfor the initial build have beenselected. Teledyne Control’sFLIDRAS software has been acquiredto read Flight Data Recorder rawdata parameters, to convert the datainto engineering units, and toperform data dumps into the data-base management system. As theflight database is built, the baselinesof various routine operations will beestablished. Knowledge-based tools,currently under development by theAPMS team, will, in later iterationswhen an adequate database isavailable, provide statistical trendingand predictive capabilities. The firstprototype system was delivered inJuly 1996 to the first airline partner.The prototype system is now opera-tional and currently being used toprocess airline flight data.

With the industry becomingaware of the capabilities of theAPMS suite of tools, the team isbeing approached by other airlinesthat had not been solicited toparticipate in the research project.So far, one additional major airlineand one major cargo airline haveasked to participate in the program.User-needs studies have beencompleted with four U.S. airlinesand a fifth has been started. Agree-ments have been signed with twoof these to cooperatively developcustomized suites of APMS tools.The APMS effort continues to workwith collaborators to improve systemdesign.

Point of Contact: I. Statler(650) [email protected]

G L O B A L C I V I L A V I A T I O N / S a f e t y

GLOBAL CIVIL AVIATION/SAFETY

Fig. 1. APMS functions.

Screening forspecial events

Statisticalanalysis

Flightanimation

Databaseexploration

Database

1997 1998 1999 200019961995

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4

Aviation Safety ReportingSystemLinda J. Connell

The Aviation Safety ReportingSystem (ASRS) solicits, processes,and analyzes aviation safety incidentreports from pilots, air-traffic control-lers and others and uses the data itcollects to further aviation safety.The ASRS (1) codifies the reports itreceives (31,096 in FY96) and insertsthem into a computer database;(2)␣ issues alerting messages onpressing safety problems describedby incoming reports; (3) providesdata retrieval services (searchrequests) for aviation safety research-ers and others; (4) publishes amonthly safety bulletin, CALLBACK,and a periodic safety journal,DIRECTLINE; (5) performs QuickResponse analytic efforts for theFederal Aviation Administration(FAA), the National TransportationSafety Board (NTSB), and othergovernmental entities; and (6) doesapplied research on aviation opera-tional problems, especially thoseinvolving human performance (seethe figure). The ASRS is heavilyreliant on information technology,and a portion of program resourcesis devoted to maintaining andupgrading that technology.

The following list is a summaryof some of ASRS’s FY96 activities. InFY96, the ASRS program:␣ ␣ •␣ ␣ Initiated an ASRS Internet site in

November 1995. Through itsWeb site, ASRS offers its publi-cations, program information,and downloadable (using anAdobe Acrobat reader) versionsof the NASA Incident ReportingForms.

␣ ␣ •␣ ␣ Accomplished a Multi-EngineTurbojet Uncommanded UpsetsStructured Callback Analysis forthe NTSB. The analysis wassubsequently adopted into theUSAir B-737 accident investiga-tion report.

␣ ␣ •␣ ␣ Completed a GPS Safety ImpactAnalysis for the FAA AssociateAdministrator of Research andAcquisitions.

␣ ␣ •␣ ␣ Accomplished a Quick Responseanalysis of Runway Transgres-sion Data for the FAA Office ofSystem Safety. These data weresubsequently presented to theFAA deputy administrator.

␣ ␣ •␣ ␣ Completed Quick ResponseNo.␣ 289 entitled “Near Mid-AirCollision Data Analysis” for theFAA Office of System Safety.

␣ ␣ •␣ ␣ Accomplished the secondinstallment of the Wake Turbu-lence Structured CallbackProject Reports; it included theanalysis of 51 wake turbulenceincidents and was submitted tothe FAA.

␣ ␣ •␣ ␣ Produced search requests for theNTSB and the FAA on DC-9cabin/cockpit smoke and aircraftequipment problems in supportof the investigation of the DC-9accident near Miami, Florida, onMay 11, 1996.

␣ ␣ •␣ ␣ Produced a Quick Responseanalysis of Part 135 AircraftIncidents for the AustralianBureau of Air Safety Investiga-tion. The data are being used todevelop a proactive aviationsafety hazard monitoring system.

Quick responsesto FAA & NTSB

Monthly safetynewsletter

Quarterly safetybulletin

Research

Safetyalerts

Databasesearch

requests

DatabaseCD ROM

Incident reports

ASRS

1997 1998 1999 200019961995

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Fig. 1. ASRS products.




5

␣ ␣ •␣ ␣ Transmitted 30 runway-incursion reports at Cleveland-Hopkins Airport, Ohio, to theFAA Office of System Safety andthe Air Line Pilots Association.As a result of ALPA and FAAfollow-up actions, revisedground-control procedures wereimplemented for departuresusing runways 23L/23R.

␣ ␣ •␣ ␣ Transmitted 24 reports to FAAand ALPA involving altitudedeviations at FUELR Intersectionon the CIVET ONE ARRIVAL toLos Angeles InternationalAirport. Subsequent investiga-tion by the FAA determined thatthe recent installation of a newILS had changed the glidepathangle at FUELR.

␣ •␣ ␣ Published one issue ofDIRECTLINE in FY96. Itsresearch articles addressedaircraft call-sign confusion andramp safety.

␣ ␣ •␣ ␣ Developed a trial version of theASRS Intranet communicationssystem. It runs on an NT Serverand is available to the ASRSstaff. The decision was made inJanuary 1996 to develop thisinternal Intranet communica-tions system based on existingInternet applications in order tolower costs and increase effi-ciency internally at the ASRS.

␣ ␣ •␣ ␣ Commenced a collaborativeresearch project betweenNASA and its French counter-part, ONERA, to evaluate anONERA human factors codingscheme and taxonomy forpossible application to ASRSincident data.

␣ ␣ •␣ ␣ Completed a conceptual andeditorial review for a secondNASA project, a study on theuse of modes in human-machineinteractions. This study, whichwas completed, made use ofASRS data.

Point of Contact: L. Connell(650) [email protected]

Crew Activity TrackingSystemTodd J. Callantine

Human operators supervisingadvanced automation systems canhave difficulties that have thepotential to compromise safety. Forexample, a recent study found thatover 44% of flight deck problemscited in a large body of incident andaccident reports were related toautomation. Autoflight systemmodes, in particular, are oftenimplicated because they can cause

unexpected behavior. One remedyis to develop technology that candetect potential operator errors andprovide the operator with context-sensitive advice and reminders. Tobe effective, such technology mustincorporate knowledge aboutoperator-automation interaction incontext; for flight deck application,this includes knowledge about modemanagement.

This research addresses anenabling technology called activitytracking, a way of inferring intent. Asthe name implies, the Crew ActivityTracking System (CATS) is anarchitecture that implements amethod for activity tracking (see thefirst figure). CATS represents knowl-edge about the operator’s tasks usingan explicit, task-analytic modelbased on the goal-based decomposi-tion of tasks into subgoals andprimitive tasks. CATS uses the modelto predict operator intentions and tointerpret subsequent operatoractions. The predictions and inter-pretations are designed to supply theknowledge required for intelligentaiding and training systems.

Constraints onoperation

Controlledsystem

Crew activity model

Humanoperators Crew

actions

Constraintson operation

Stateinformation

Contextspecifiers

Interpretations

[to aid or training system]

Predictions

Actionmanager

CATS

OFM-ACM

Fig. 1. The Crew Activity Tracking System in context.


6

CATS was implemented to trackthe activities of Boeing 757 pilotsusing autopilot flight modes undernormal operating conditions. Anexperimental evaluation was con-ducted to assess the effectiveness ofthe CATS method. Ten type-ratedline pilots from a major airlineparticipated in the study. Each flewfive experimental scenarios on areal-time part-task simulation of theBoeing 757. Of the 2,089 pilotactions detected in the study, CATScorrectly interpreted 81%. A subse-quent analysis identified adjustmentsto the CATS model and processingscheme that would allow CATS tocorrectly interpret 94% of pilotactions.

Current research seeks to extendthe capabilities of CATS and toexplore new applications. Specifi-cally, the objective is to enableCATS to predict and interpret theactions of two-person crews by usingcomplex functions of the FlightManagement Computer Control andDisplay Unit (FMC CDU), and data-link communications. These activi-ties are critical for procedures that

are being developed for use withnew air-traffic control automation.

The second figure shows asimplified task decomposition fromthe enhanced CATS model, fromwhich most cognitive, verbal, andperceptual activities are omitted. Thetask shown supports a new descentprocedure that uses an assigneddescent point (“adp”), in addition tothe top-of-descent point computedby the FMC. When the crew hasbeen cleared for the procedure,CATS uses this portion of the modelto predict and interpret the CDUprogramming activities required toperform the task. For example, CATSfirst predicts which pilot is respon-sible for programming the assigneddescent point to go to the CDULEGS page. CATS next predicts thata reference way point will be built inthe CDU scratchpad, then line-selected to the appropriate place onthe LEGS page, and so on. As theseactions are performed, CATS checksthe entered values for accuracy andthen either interprets the actions tosupport the task of entering the

assigned descent point or signals apotential error.

A Boeing 747-400 simulatorstudy to investigate pilot perfor-mance on a new descent procedurewas conducted at Ames ResearchCenter. The data show that althoughpilots performed the new procedureeffectively in most cases, there werestill a number of compliance viola-tions. These data are used to investi-gate a new application of CATS:tracking crew activities to automati-cally identify departures from theprocedure and capture the contextin which these departures occurred.With this information, the proceduremay be refined to address problems,and thereby improve compliance.

Point of Contact: T. Callantine(650) [email protected]

Study of Line OrientedFlight TrainingKey R. Dismukes

Airlines train pilots to worktogether as safe, efficient crews byusing a realistic full-mission flightsimulation approach called LineOriented Flight Training (LOFT). Inthis annual recurrent training, crewsencounter challenging situations thatthey must manage by coordinatingtheir efforts, exercising good judg-ment and decision-making, anddrawing upon all availableresources. After the LOFT, theinstructor leads the crew in adebriefing in which they areexpected to analyze what happened,evaluate their own performance,

Fig. 2. A simplified task decomposition from the enhanced CATS model.

enter-ctas-adp-ref-dist

build-ctas-adp-ref-dist

enter-ctas-adp-ref-wpt

build-ctas-adp-ref-wpt

access-LEGS-pg

verify-ctas-adp

execute-ctas-adp

program-ctas-adp

put-ref-dist-LEGS-pg

put-ref-dist-scr-pad

put-ref-wpt-LEGS-pg

put-ref-wpt-scr-pad

push-LEGS-key

SOP-talk

push-EXEC-key




7

and identify ways to improveperformance. Because the LOFT is avery busy, intense experience, howmuch the crews learn from the LOFTand take back to line operationshinges on the effectiveness of thedebriefing.

Both the airlines and the FAAespouse the idea that LOFT instruc-tors should refrain from lecturing thecrews in the traditional “teacher-tell”manner. Instead, instructors areencouraged to “facilitate” self-analysis by the crew so that they willlearn more deeply. However, therehas been little study of how tofacilitate this self-analysis; as aconsequence, the airlines have nothad good data-based techniques fortraining their instructors in debriefingprocedures.

Human factors scientists atAmes recently completed a study,in collaboration with major U.S.airlines, to evaluate LOFT debrief-ings and to provide guidelines fortraining instructors. The studyevaluated the effectiveness of LOFTdebriefings at a cross section ofairlines, analyzed facilitationtechniques, and identified commonerrors. The study demonstrated thatinstructors who are effective infacilitating self-analysis substantiallyincrease the depth of crew participa-tion and self-analysis; however,individual instructors differed greatlyin their effectiveness as facilitators.

In conjunction with the techni-cal report of the study, the researchteam prepared a detailed manual foruse in training instructors to facilitatedebriefings. This manual explainsthe concepts of facilitation, describeseffective techniques, explains how

and when to use these techniques,and shows how to engage crews thatdo not initially respond. Immediatelyafter receiving the study materials,several major airlines reprinted themanual for the use of their instruc-tors. Other airlines have overhauledtheir training of instructors toincorporate the findings from thestudy; they later reported significantbenefits to their crew trainingprograms.

Point of Contact: K. Dismukes(650) [email protected]

Measuring Air TrafficComplexityIrene V. Laudeman, Connie Brasil,Robert Branstrom

An important goal in advancedair-traffic operations is that ofproviding more system flexibility tothe user. The idea of sharing theresponsibility for aircraft separation,in which pilots and air-trafficcontrollers work together to ensureseparation, is designed to providesuch flexibility. Currently, underinstrument flight rules the air-trafficcontroller is tasked with ensuring theproper separation of aircraft. Undershared separation-responsibilityprocedures, pilots in appropriatelyequipped aircraft would assumesome responsibility for the manage-ment of aircraft separation. Theproportion of responsibility assignedto pilots and air-traffic controllers

would be a function of the complex-ity of the airspace.

Shifts in operational procedureswill be specified as a function ofairspace complexity, making thedevelopment of separation proce-dures dependent on the develop-ment of a complexity metric. Thecomplexity of air-traffic patterns, andhence the workload related to themanagement of air traffic, is knownto include more than a simple countof aircraft contained in a volume ofairspace. However, the trafficcomplexity factors beyond that ofaircraft number have not beenclearly identified, nor has anyrelationship among the factors beenestablished.

A human-in-the-loop simulationstudy was conducted to evaluatethree modes of separation responsi-bility and to provide data for use indeveloping a complexity metric. Tengroups of four currently qualified air-traffic controllers participated in ninesimulation scenarios. In each groupone participant acted as the control-ler in a sector of airspace and threeparticipants acted as pilots.

Aircraft data in the form oflatitude, longitude, heading, altitude,and speed were collected for all ofthe aircraft in each of the nine30-minute scenarios. The complexityof the simulated airspace wascomputed from the aircraft data atevery 2 minutes of the 30-minutescenarios. Complexity functionswere computed as a sum of trafficfactors that included aircraft count,aircraft converging at the samealtitude, and aircraft changingheading, speed, or altitude.


8

The complexity functionspredicted an operational shift relatedto the sharing of separation responsi-bility (see the figure) indicating thatsuch functions might be useful inspecifying shared separation respon-sibility procedures.

Point of Contact: I. Laudeman(650) [email protected]

Operational Interventionsto Human Error in AircraftMaintenanceBarbara G. Kanki, Vicki Dulchinos

A significant proportion ofaviation accidents and incidents areknown to be tied to human error.However, research of flight opera-tional errors has shown thatso-called “pilot error” often involvesa variety of human factors issuesand not a simple lack of individualtechnical skills. In aircraft mainte-nance operations, there is similarconcern that maintenance errorswhich may lead to incidents andaccidents are related to a largevariety of human factors problems.

Although industry initiatives involv-ing human factors training inmaintenance have become increas-ingly accepted as one type ofmaintenance error intervention,there remains a dual challenge:(1)␣ to develop human factors inter-ventions that are directly supportedby reliable human error data, and(2)␣ to integrate human factorsconcepts into the procedures andpractices of everyday technical tasks.

These challenges are beingaddressed at Ames Research Center.First, industry-wide incidentsreported to the Aviation SafetyReporting System are being analyzedin order to identify and characterizehigh priority problem areas. Whenanalyzed for contributing factors, atleast 50% of the incidents involvedmore than one technician—othermaintenance personnel, flight crewmembers, and airport personnel.

Consistent with these findings,research is being conducted thatfocuses on human factors interven-tions related to practices andprocedures; namely, structuredon-the-job training and procedurere-design. In both areas, particularattention is being centered on areasin which maintenance tasks requirecoordination both within andbetween maintenance teams.

In the area of structured on-the-job training, field applications ofthe Task Analytic Training System—a performance-based system thatinvolves full workforce participationin its design, development, andimplementation—have beenconducted.

8 10 12 14

Scenario 1 shared (3)Scenario 1 shift

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Fig. 1. Air-traffic complexity functions and points at which separationresponsibility was shifted for two types of traffic scenarios.




9

Human factors principles mayalso be incorporated into themaintenance procedures themselves.When Boeing modified its B-737CFM56-7 engine-change procedure,the efficiency of the engine-changeprocess was significantly improved.A 14% increase in efficiency,attributed to changes in the mainte-nance manual alone, presented anopportunity to conduct a systematiccomparison between original andrevised procedures. The goal was toanalyze the specific modificationsthat led to the improvement inefficiency and to identify the contri-bution of human factors. Some

results of this item-by-item compari-son are found in the summary offunctional changes shown in thefigure.

Finally, a collaborative relation-ship has been established with thehuman factors team at KennedySpace Center; a series of workshopsfor discussing human factors issuesin aviation and space vehiclemaintenance is being conducted.The first workshop was held at AmesResearch Center in September 1966;it focused on error analysis (inci-dents, accidents, mishaps, and close-calls). This workshop facilitated the

free exchange of human factorsinformation between aircraft andshuttle maintenance operations.

Point of Contact: B. Kanki(650) [email protected]

Aircraft SeparationRisk ModelMary M. Connors

Increased demand for air traveltranslates into a need to accommo-date more aircraft in the terminalairspace. Separations betweenaircraft pairs must be small enoughto be efficient while remainingsufficiently large to be safe. Presentseparation standards are consideredsafe for the equipment and condi-tions that presently prevail. It ispossible that new technologies couldresult in maintaining the presentsafety level while permitting thedistances between aircraft pairs tobe reduced. What is needed is aquantitative method of evaluatingsafety. The objective of this researchis to develop a computer model thatwill provide this link betweenaircraft separation and a quantitativemethod of assessing safety risk.

The model, called the ReducedAircraft Separation Risk AssessmentModel (RASRAM), evaluates safetyrisks for a variety of flight scenariosrelating to final approach, landing,and rollout for parallel and singlerunways. The basic approach ofRASRAM is to quantify the riskassociated with current separationstandards and to then compare itwith that for reduced separation

Fig. 1. Distribution of reason codes in the revised procedure(N = 735 procedural steps).

A. 5%

B. 8%

C. 12%

D. 4%

E. 19%

F. 33%

X. 19%

A. Situation awareness/Time task management (n=38)

B. Planning/Communication-new resources (n=62)

C. Planning/Communication of task sequence (n=85)

D. Clarification/Formatting - Simplified English (n=28)

E. Clarification/Formatting consistency (n=139)

F. Process improvement (n=243)

X. No functional change (n=140)


10

operations during instrumentmeteorological conditions, consider-ing procedural and technologicalchanges. The research is beingperformed for Ames Research Centeras an integral part of NASA’s Termi-nal Area Productivity (TAP) program,and in coordination with the FederalAviation Administration.

RASRAM includes the followingtwo scenarios that measure the effectof separation on safety: lateralseparation for parallel approaches;and in-trail separation during singlerunway operations, accounting forrunway occupancy and wake vortexeffects. The figure illustrates theparallel approach scenario, forwhich independent approaches toparallel runways constitute theoperational context. The primaryseparation criterion is the distancebetween the runway centerlines forthe two approach paths. The defin-ing characteristic of the scenario inthe model is a blundering aircraftthat strays from its own finalapproach, crossing the path of theother approach stream. The safety ofthe scenario (for current operations)

is determined (1) by the performanceof the controller in detecting theblunder and issuing breakoutinstructions to the evader aircraft,and (2) by the performance of thepilot and aircraft in completing theevasive maneuver. RASRAM modelsall of these effects and quantifies thesafety of the operation. The standardrisk measure is the probability thatthe blundering aircraft will approachwithin 500 feet of an aircraft in theother approach stream.

NASA’s TAP Program anticipatesprocedural changes for terminal-areaoperations along with the introduc-tion of new technologies. These newtechnologies include DifferentialGPS (DGPS), Automatic DependentSurveillance (ADS-B), and severaltechnologies under development bythe NASA TAP program: the Center-TRACON Automation System(CTAS), the Aircraft Vortex SpacingSystem (AVOSS), the DynamicRunway Occupancy Measurement(DROM), and the Airborne Informa-tion for Lateral Spacing (AILS).RASRAM begins the process of

quantifying the safety risk associatedwith the effects of these technologieson separation standards. The modelcan also be used to provide arelative comparison of the safety ofproposed new procedures with thesafety of current operations andtechnologies. Using RASRAM, thesafety of further separation reduc-tions for parallel approaches thatrely on new technologies can beanalyzed and compared with currentprocedures. Similarly, the safety ofreductions of in-trail separation canbe compared with current proce-dures. Although it is being devel-oped for initial application to finalapproach and landing, the basicapproach to modeling separationrisk has direct application to allphases of flight. The potentialapplication of these models to enroute and approach airspace is beingundertaken in the Advanced AirTransportation Technology programat Ames.

Point of Contact: M. Connors(650) [email protected]

Runwayseparation

Blunder path

MD = miss distance

Evader aircraft

No transgression zone

3° Glide path

Blunder aircraft MD

Fig. 1. Parallel approach lateral separation geometry.




11

The Final ApproachSpacing ToolTom Davis

The Center/TRACON Automa-tion System (CTAS) is an air-trafficcontrol automation system underdevelopment at Ames ResearchCenter. The system is designed tosupport increasing demands forcapacity and efficiency in theNational Airspace System. Theterminal-area component of thesystem, the Final Approach SpacingTool (FAST), is designed to assistterminal air-traffic controllers inefficiently managing and controllingarrival air traffic for the last 40 milesof flight down to the runway. TheFAST system issues the controllersa series of sequencing, runway,heading, and speed advisories toachieve an efficient flow of trafficthat increases airport capacity,reduces delays, and reduces control-ler workloads.

The objective of the researchand development effort is to test theFAST system operationally in a seriesof phased functionality enhance-ments at the Dallas/Fort WorthTRACON (Terminal Radar ApproachControl) (see figure (see ColorPlate␣ 1 in the Appendix)). Theoperational field testing of the FASTsystem allows researchers to furtherdevelop and assess the system withthe end-users, that is, with the air-traffic controllers. The assessmentsinclude a series of observations withthe FAST system operating in ashadow mode on live traffic data,real-time simulation evaluations of

the FAST system at Ames and at theFAA Technical Center, and a limitedoperational assessment of theFAST system functionalities atDallas/Fort Worth.

Development and field testing ofthe FAST system achieved a signifi-cant milestone during FY96; the“Passive” FAST functionality, whichincludes the sequence and runwayadvisories, underwent operationaltesting at the Dallas/Fort WorthTRACON. The tests, which wereconducted in cooperation with theFAA, the National Air Traffic Con-trollers Association, and the AirlineTransport Association, began inJanuary 1996 and continued throughJuly 1996. The objectives of the testwere: (1) to confirm the technicalperformance of the Passive FASTfunctionalities, (2) to assess theairport delay and capacity benefitsof Passive FAST, and (3) to assessthe controller workload benefits ofPassive FAST. The testing demon-strated an arrival rate improvementat Dallas/Fort Worth of 13%, adeparture queue backlog reductionof 9%, and an overall increase intotal airport operations (arrivals anddepartures) of 13%, all with noincrease in taxi times and withlittle or no increase in controllerworkload. The system has receivedoverwhelmingly positive supportfrom all participants.

The Active FAST systemfunctionalities, including speed andheading advisories, remain to bedeveloped and operationally evalu-ated. The Active FAST system willundergo operational testing similar

to that of the Passive FAST before anational deployment system isspecified.

Point of Contact: T. Davis(650) [email protected]

Air/Ground IntegrationR. Slattery

The Center/TRACON Automa-tion System (CTAS) was developedfor use in the air traffic-controlenvironment. As part of the TerminalArea Productivity Air Traffic Man-agement program, research hasbegun to expand CTAS to coordinatewith aircraft that are equipped withFlight Management Systems (FMSs)using data-link. A large portion ofthe commercial aircraft fleet is soequipped and many older aircraftare being retrofitted with an FMS.However, busy air-traffic controllersdo not often allow pilots to fullyutilize the FMS. An FMS calculatesthe most efficient trajectory, thussaving fuel, and then follows thetrajectory very accurately, increasingtrajectory prediction accuracy. Thus,if the CTAS helps the controllers takeadvantage of the FMS trajectory, theperformance of the airspace systemshould be improved.

The objectives of the researchand development effort are toquantify the actual benefits of theair/ground system with both control-lers and pilots in the loop. Theoreti-cal benefits have been studied,under the assumption that thetrajectories are followed with the


12

maximum accuracy possible for theFMS. These benefits may be dimin-ished, however, by the extraworkload imposed on the controllersand pilots; also, they may not berealizable because of operator error.

A piloted simulation wasperformed using the CVSRF 747-400simulator. Since the simulator wasnot equipped with data-link at thetime, the routes were defined asstored arrivals in the FMS (anexample is shown in the figure).The pilots were issued FMS routechanges, while still performing therest of their normal duties. For abaseline comparison, equivalentroutes were flown using currentcontroller clearances. The aircraftwas flown in the Dallas/Fort Worthterminal area, starting at the two

eastern arrival gates into theTRACON (Terminal Radar ApproachControl) and finishing at the runway.The accuracy of the horizontal routeincreased for the FMS cases, but thevertical predictability was lower.This was because the vertical portionof the FMS route is entered ascrossing altitudes at way points. Aslong as the pilots meet the requiredaltitude, the point at which theybegin their descent and the way inwhich they make the descent areopen. Offsetting the achievableaccuracy, the pilots felt that the FMSroute changes produced far moreworkload with current generationFMS systems than did currentprocedures. They also expressedconcerns about the amount ofheads-down time spent loading the

trajectory while in the busy terminalarea. There were also more errors inloading and in following the FMSroute, though these should bereduced by data-link and by inter-face changes to the FMS.

Point of Contact: R. Slattery(650) [email protected]

The Traffic ManagementAdvisorHarry N. Swenson

The growth of commercial airtravel within the United States hasput a severe strain on the nation’s airtraffic capacity. This, coupled withthe “hub-and-spoke” proceduresused by the major air carriers andthe marketing requirements foraircraft to take off and land atoptimum times, has required animprovement in the Air TrafficControl System. The Center-TRACON Automation System (CTAS)is a decision-support concept beingdeveloped to improve airportcapacity and to reduce delays whilemaintaining controller workload ata reasonable level. The extendedterminal-area component of thesystem is the Traffic ManagementAdvisor (TMA). The TMA is a time-based strategic planning tool thatprovides traffic management coordi-nators and en␣ route air trafficcontrollers the ability to efficientlyoptimize the capacity of a demand-impacted airport. The TMA consistsof trajectory prediction, constraint-based runway scheduling, traffic

KINGGREFLE2: Cross at 210K

IAS. Cross at 4,000'

17LGT

JIFFYCross at 170K IAS

REFLE1

REFLE2 NOVEL

SWIFTREFLE1: Cross at 210K

IAS. Cross at 4,000'

SEAGOCross at 250K IAS.

Cross at 11,000'

SCY

REFILCross at 210K IAS.

Cross at 11,000'

Fig. 1. Scurry FMS arrivals, REFLE1 and REFLE2.




13

flow visualization, and controllerarrival sequence, time, and delayadvisories.

The TMA and all other CTAStools are being developed to demon-strate user benefits both to air-trafficcontrollers and commercial aircarriers. Air-traffic control is a verycomplex multivariable problemrequiring teams of highly skilledindividuals to safely and efficientlymove traffic from terminal departurepoint to terminal arrival. Thisextended complexity requires thatautomation aids designed to assistthese teams be proven and validatedin actual operations. The objectiveof the TMA 1996 research anddevelopment effort was focusedtoward an operational evaluationat the Ft. Worth Air Route TrafficControl Center, Ft. Worth, Texas.The evaluations also focus researchinto areas and concepts that provideuser benefits.

The TMA achieved severalmajor milestones in this focusedeffort toward operational evalua-tions. The first was controller andoperational hardware in-the-loopsimulations at the William J. HughesFAA Technical Center with theNational Air Traffic ControllersAssociation (NATCA) Ft. WorthCenter System Design Team. Thiswas followed by the installation andcheckout of the TMA hardware/software components at theFt. Worth Center, the nation’s fifthbusiest Center, which manages andcontrols traffic into the secondbusiest airport in the world (Dallas/Ft. Worth). Upon completion of thesystem installations, on-site shadowevaluations and nighttime simula-

tions were conducted. Subsequently,the formal operational evaluationswere conducted. The TMAdemonstrated delay reductions of1–2 minutes per aircraft, as well asa significant reduction in controllerworkload. The original plan was toremove the TMA upon completionof the formal evaluation, but, basedon the benefits achieved, the FAA,the Air Transport Association, andNATCA requested that NASAoperationally support the TMA on acontinuous basis. NASA has com-plied with that request, and the TMAhas been used operationally sincethe completion of the formal evalua-tions. Since the evaluations, a 10%capacity increase has been attributedto TMA operations.

Point of Contact: H. Swenson(650) [email protected]

Surface MovementAdvisorBrian J. Glass

Recurrent delays during depar-ture taxiing at large airports havebecome commonplace with theprevalence of “hub-and-spoke”airline operations, as large numbersof aircraft attempt to land, taxi, beserviced, taxi, and depart, all within60–90 minute “banks.” Airfieldtower controllers strive to avoidimbalances and bottlenecks byintegrating data from visual cuesand from a variety of other sources.However, lengthy, imbalanced taxi

queues are evidence that althoughsufficient and safe, the controller’smental planning process (givencurrent data sources) is not necessar-ily optimal. By providing data fusionand automated optimal taxi planadvisories to the ground controller,the controller can operate withimproved data-gathering andplanning capabilities. Improveddynamic taxi routing, and hencesmoother airport operations withless surface taxi delay should result.Eventual national implementationof the Surface Movement Advisorsystems (SMA) at the 13 largest U.S.airports is projected to save users atleast 5% of the $1.6 billion annualground-delay costs incurred as aresult of inefficient taxi and runwayqueuing—based on recent FAAsimulations and Air TransportAssociation cost figures.

The SMA is a series of succes-sive airfield data systems that isbeing developed as a joint effortbetween Ames Research Center andthe Federal Aviation Administration(FAA). The first proof-of-conceptSMA (Build-1) electronically con-nects the air-traffic control, airline,and airport operations users atAtlanta-Hartsfield airport (ATL) tofacilitate information-sharing anddata fusion. SMA Build-1 has beenin use on a daily basis at ATL byairlines and airport ramp towerssince June 1996 and was broughtonline in the FAA control towerin September 1996. The figureshows an overview of the SMAsystem that was deployed to Atlantain 1996.


14

Running in a commercialtransaction-processing database onan off-the-shelf UNIX server, theSMA software currently contains itsown tracking, time estimation, datafusion, monitoring and predictionsoftware modules. SMA furnishesdata as an ASCII text stream toairline servers, or as separateX/Motif-based touchscreen-capablegraphical-user interfaces for the FAA,airline, and airport operationspersonnel.

Point of Contact: B. Glass(650) [email protected]

Simplified Vision Modelsfor Display QualityAssessmentAl Ahumada

Detection and recognition ofobstacles (aircraft, trucks, etc.) iscrucial for safe aviation operation inthe terminal area. Vision models canmake an important contribution todisplay design by allowing computa-tional predictions of the visualadequacy of potential designs forobstacle detection and recognition.The first figure shows a pair ofsimulated display images, one(panel b) with an obstacle on therunway and one without. Investiga-tors have been measuring the ability

of human observers to make suchdiscriminations and have beenconstructing and testing computa-tional models to predict theirabilities.

Image discrimination modelsthat have been used as image-qualitymetrics range in complexity fromsingle filter models to multiple-channel models with channels thatare selective in spatial frequency andorientation. The simple filter modelscan be thought of as representing thevisual information at precorticallevels of the visual system. Thesemodels can predict the variations inthe visibility of targets that occur asthe target spatial frequency changes.The multiple-channel models

Fig. 1. Overview of the SMA system deployed to Atlanta in 1996.

LockheedValuJet

Other airlines

DeltaAirlines

City of Atlantaairport authority

Performancehistograms

Predictionalgorithms

Airport operationsprocedures

Statisticalanalysis

Outputmanager

SMA server

Inputmanager

Monitoring andpredictions

Highspeednetwork backbone

Flight plans

FAAtower Real-time

radar data

Weatherdata

Real-time aircraftstatus updates

Airlineschedules




15

simulate the orientation and spatialfrequency selectivity of cortical cells.Because the channel outputs arenonlinear, the channel modelspredict masking of targets in high-contrast image regions. For example,the channel models outperformcontrast-sensitivity filter models inpredicting the detectability of targetsin a natural background.

Some recent vision modelsinclude between-channel interac-tions that allow the models topredict masking from image compo-nents exciting different channelsfrom those responding to the target.These models have even greatercomputational complexity. Assum-ing homogeneity of these interac-tions leads to a simple contrastmasking correction. The secondfigure diagrams the image discrimi-nation model that results from

applying this correction to acontrast-sensitivity filter model. Incomparing the predictions of thismodel with those of the complexmodels, it is found that the simplemodel predicts human visualdetection performance just as well.

Point of Contact: A. Ahumada(650) [email protected]

Perceptually Tuned VisualSimulationMary K. Kaiser

Human factors engineering isrequired to improve the quality ofvisual displays in aerospace systems.Advanced computer-generatedimagery (CGI) systems are used tocreate compelling visual displays fornavigation/control systems, vehicle/system simulation, telerobotics, andscientific visualization applications.The quality of these displays canaffect the safety and productivity offlight and ground-based operations.Inevitably, the realism of thesedisplays is constrained by limitationsin CGI hardware and software,especially if images need to begenerated in real-time. Despiterapid advances in image-generationtechnology, human operators desiremore realistic, higher-fidelitydisplays; it is likely that this demandfor improved fidelity will continuefor the foreseeable future.

Research is being conductedto examine techniques aimed atreducing the computational costrequired to achieve a desired level ofimage quality and frame rate. These

CSF

Background

Target +Background

RMS

C=1

1n

nfi

2Σ

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CSF

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1

ndi

2Σ

XX

d'

(a)

(b)

Fig. 1. Panel (a) is a 128 x 128 pixelgray-scale digital image of asimulated airport runway scene.Panel (b) shows the runway scenewith an aircraft obstacle.

Fig. 2. Schematic of the simple image discrimination model. At the left, theupper image is the background image and the lower image is the target-plus-background image. After the luminance images are converted to contrastimages (a step not illustrated), the contrast images are filtered by a contrastsensitivity function (CSF). On the top path, the masking parameter c is therms value of the background-filtered contrast values fi. On the bottom path,the corresponding filtered values from the image are differenced and thevector length of these di values is divided by the contrast factor to get thepredicted number of just-noticeable-differences between the two images.


16

techniques exploit principles ofvisual processing to reduce thecomputational load. This multi-disciplinary research involves acollaboration among researchscientists at the Ames ResearchCenter; professors in computerscience at Carnegie Mellon Univer-sity and in psychology/biomedicalengineering at the University ofVirginia; and designers and engi-neers at various industry sites.

A set of techniques has beendeveloped for rendering images withenhanced apparent resolution.NASA has applied for a patent forthis process (NASA Case: ARC12080-1). In using this process tocreate stereo displays, images withdifferent resolutions are shown to thetwo eyes; examples of this techniqueare shown in the figures below. Thefirst figure demonstrates varyingtexture complexity; the second

demonstrates varying polygonalcomplexity. The resulting fusedimage appears to possess the higher-resolution detail. User studiesconducted with these “hi-lo” stereodisplays indicate that people areable to extract stereo-specified depthwith these displays about as well asthey do with traditional (“hi-hi”)displays. Further, no interferencewith normal stereo vision resultsfrom exposure to the hi-lo displays.

Present efforts focus on furtherevaluation of the algorithms, theextension of techniques to largerobject classes, and the developmentof generalizable tools suitable forinclusion in a graphics modelingtoolbox. Coordination with hard-ware and software developers seeksto maximize the utility of thesetechniques and to ensure compat-ibility with hardware architecture.

The development of a number ofrendering techniques that signifi-cantly enhance the performance ofgraphics systems is expected. Thegoal is to both extend the upperrange of graphical rendering perfor-mance and to enable lower-endsystems to produce visual imagerythat currently can be produced onlywith high-end systems.

Point of Contact: M. Kaiser(650) [email protected]

Fig. 1. Only the image presented to the left eye in this stereo pair has texturemapping. Nonetheless, the resulting stereo percept appears textured.

Fig. 2. Another example of “hi-lo” stereo images. Here the left image iscreated with far more detail (that is, a larger number of polygons is used tomodel the object) than the one on the right. The resulting stereo perceptionappears high resolution.




17

Entropy Masking in VisualDisplaysAndrew B. Watson

As part of NASA’s HumanExploration and Development ofSpace Enterprise and Aeronauticsand Space Transportation Technol-ogy Enterprise, the Vision Scienceand Technology Group at AmesResearch Center is doing research onthe human factors of visual displaysand visual communication systems.A primary thrust of this effort is todevelop computational models ofhuman visual performance that canbe used in the engineering design ofimaging and display devices. A firstgoal of human vision models is topredict visibility of arbitrary targets,especially against noisy or clutteredbackgrounds that are typical of realimaging environments. This problemis central to applications such asimage compression, flat-paneldisplay design, sensor fusion, anddesign of helmet-mounted and otherhead-up displays. To meet thischallenge, a program has beeninitiated involving experiments onvisual masking: the interference ofthe background with the detection ofvisual targets.

As a result of this research, anew category of visual masking hasbeen identified; it is called entropymasking. Previous research overmany decades had identified twoprincipal varieties of visual masking:contrast masking and noise masking.The former refers to a reduction invisual sensitivity resulting from apassive adaptive process. In effect,the gain of visual neurons is turneddown when there is a large amountof pattern stimulation, in order to

prevent saturation of the limiteddynamic range of the neuralresponse. Noise masking refers toan inevitable reduction in visibilitywhen a random component is addedto the visual stimulus. Entropymasking depends on neither gaincontrol nor randomness. Instead, it isdue to the observers lack of knowl-edge about the obscuring back-ground, and it may be amelioratedby increasing that knowledgethrough learning.

The following experimentsillustrate the essentials of entropymasking. The observer attempted todetect the Gabor-function targetpictured in part (a) of the first figure;the target was obscured by theaddition of one of the masks shownin parts (b) and (c). The mask shownin part (b) is a cosine luminancegrating with the same spatial fre-quency as the target, and that shownin part (c) is a sample of one-octave,bandpass noise with a center spatialfrequency equal to that of theGabor-function target. The twomasks were equated in contrastenergy so that they would haveequal effects on the contrast gain-control system, that is, equivalentcontrast masking.

On each trial, the observerreceived two brief presentations ona cathode-ray-tube monitor. Onecontained a background only, theother contained a background plusthe target. The observer tried toidentify the presentation containingthe target. The contrast of the targetwas varied from trial to trial in orderto estimate the contrast requiredfor 82% correct performance. Tomanipulate the degree of random-ness, the bandpass mask was(1) new on each presentation

Fig. 1. Visual target (a) and twomasks: cosine grating (b) andbandpass noise (c). Each mask isshown with the target added.

(a)

(b)

(c)


18

(random condition), (2) the samefor both presentations of a trial butnew for each trial (twin condition),or (3)␣ always the same (fixedcondition).

The results are shown in thesecond figure. The cosine maskelevates the target threshold by asmall amount (about 3 decibels), butthe random condition producesmuch more masking. However, thetwin condition shows that thismasking is not due to randomness,since the masks are identical in thetwo presentations of each trial. Thefixed condition shows that withlearning (640, 2176, and 3584 trialswere collected from the threeobservers), a significant reduction inmasking is obtained. Indeed, at theend of learning, the threshold issimilar to that for the cosine condi-tion. It can be concluded that the

masking effect of the bandpass noiseis due to the observer’s ignoranceabout its structure (its entropy).

It is thought that entropy mask-ing is the dominant form of maskingin many applied situations. Conse-quently, it is important to verify itsexistence and properties in order toenable optimal design of visualcommunications systems. This workmoves NASA closer to its goal ofdeveloping a set of general humanfactors engineering tools that willenhance the safety and effectivenessof its Space and Aeronauticsmissions.

Point of Contact: A. Watson(650) [email protected]

Fig. 2. Target thresholds as a function of mask condition.

Cos Random Twin FixedNone

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Vertical Motion SimulatorAdvanced SimulatorNetworkWilliam B. Cleveland

The Advanced SimulatorNetwork (ASN) is an integration ofnewer and higher-performance hostcomputers and real-time dataacquisition networks into theVertical Motion Simulator (VMS)complex at Ames Research Center.The system provides significantlybetter performance while retainingthe powerful functionality of theprevious system. As shown in thefigure, the system consists of the datanetwork, instrumentation input/output (I/O), and a host computertogether with its interface to thenetwork. In a simulation setting, thepilot’s controls are input through theCockpit CAMAC (Computer Auto-mated Measurement and Control)I/O, passed via the Data Highwayand VME interface to the hostcomputer where the aircraft’sresponse is computed and returnedvia the network highway elements tothe motion, cockpit display, andlaboratory display devices.

The performance increase of theoperational systems is dramatic. Bythemselves the computers are twiceas fast as the computers of just4–5 years ago. Testing of the newCAMAC instrumentation shows afactor of 10 speed-up in perfor-mance over that of the old hardware.These improvements reduce timedelays that cause a simulated aircraftto lose stability in comparison withthe real aircraft. When there is noreal aircraft for comparison, incor-rect conclusions are often made




19

when the simulator uses poorequipment or techniques. Althoughthe VMS system can operate at1000 hertz when only I/O is per-formed with the motion, laboratory,and cockpit subsystems, adding thetypical aircraft model allows a200-hertz operation. Most simula-tions are near the 60-hertz rate of theassociated graphics generators, butthe ASN system performance reservewill allow larger model options andI/O rates when needed.

Early in FY96, the first of thesystems was installed into anInterchangeable Cab fixed-basesimulation laboratory, where it wastested and perfected before it wasinstalled into the VMS. Before theend of FY96, the VMS system hadbeen used in five simulationsincluding astronauts flying the spaceshuttle vehicle.

Point of Contact: W. Cleveland(650) [email protected]

Intelligent Aircraft ControlSystemCharles C. Jorgensen

The intelligent aircraft controlsystem provides a safety-orientedflight control technology that canefficiently deal with off-nominal andunforeseen changes in aircraftsystems or operating environments.The effort accomplishes reconfig-urable flight control under damagescenarios by using a modified F-15aircraft’s (ACTIVE) differential canardand vectored thrust capabilities. Thiseffort is a four-year cooperativeresearch contract begun in 1995.It comprises three phases: Phase I,create neural nets (NNs) that modelstability and control derivatives inthe pitch, roll, yaw, lift, and sideforce axes of the F-15 ACTIVEaircraft in 1995–96 (see the figure(see Color Plate␣ 2 in the Appendix));Phase II, develop on-line NNs toprocess aircraft sensor data in real-time and update the stability andcontrol derivatives in 1997; and

Phase III, flight demonstration ofreal-time NN control and accidentreconfiguration (1997, 1998).

In 1996 major progress wasmade. Phase I NNs were generatedthat match the ACTIVE aerodynam-ics and were programmed into theF-15E computer. Three Phase I NNswere produced: (1) the Leavenburg-Marquardt network at AmesResearch Center (ARC), (2) an activeselection net at McDonnell DouglasAircraft Corporation (MDAC), and(3) a neural fuzzy (ANFIS) atTennessee State University.

Four second-generation on-linenetworks were developed forPhase II: Radial Basis Networks(MDAC), Recursive Higher OrderNeural Network (WashingtonUniversity), Feedback LinearizationNeural Net (ARC), and Dynamic CellStructures (ARC).

Two on-line aerodynamicderivative estimation methods weredeveloped by MDAC: KalmanFiltering/Recursive Prediction andLocally Weighted Regression. ThreeLinear Quadratic Regulator Methodswere designed by MDAC: (1) RobustServo, (2) Setpoint Regulator, and(3)␣ SOFFT, Langley Research Center.A full-scale parameter sensitivityanalysis was begun for performanceenvelope, stability, and robustnessusing the new techniques. A real-time Ricatti equation solver wasdeveloped (MDAC), and a newVirtual Reality test environment wasdeveloped by ARC using a nonlinearF-15E model.

Point of Contact: C. Jorgensen(650) [email protected]

CAMAC I/O

MotionLaboratory Cockpit

Data "highway"Dec AlphaVME I/F

Fig. 1. Advanced Simulator Network.


20 G L O B A L C I V I L A V I A T I O N / A f f o r d a b i l i t y

GLOBAL CIVIL AVIATION/AFFORDABILITY

Facilitating User RoutePreferences in En RouteAirspaceBob Vivona, Mark Ballin,Steve Green, Ralph Bach,Dave McNally

Under the current air-trafficsystem, aircraft generally must fly onfixed routes. On the other hand, theAir Transport Association estimatesthat its member airlines could save$1.2 billion per year if they wereable to fly direct routes. However,relaxing existing routing restrictionswill require new conflict-predictionand resolution automation to helpcontrollers maintain requiredseparation while minimizing theireffect on their workload. Althoughsome automation now exists (forexample, Conflict Alert, which usesa 2-minute prediction based onprevious radar hits), for the most partair-traffic controllers detect conflictsby visually monitoring radar tracksand, when necessary, issuingresolution advisories to aircraft toavoid loss of separation (5 nauticalmiles horizontal, 2000 feet vertical).Conflict-prediction and resolutiontools for controllers are beingdeveloped under the Advanced AirTransportation Technology programat Ames Research Center. Theobjective of this work is to developan operational concept and associ-ated software for use of conflict-prediction information in order togenerate minimum-cost resolutionadvisories to facilitate increaseduser route preference in en routeairspace.

A wide range of traffic environ-ments is found in the NationalAirspace System. At one extreme isen route airspace away from busyterminal areas consisting of aircraftgenerally not constrained by trafficor weather. If traffic density is low,very little ground-based air-trafficcontrol intervention is required. At

the other extreme is the en routearea near busy terminal areas whereaircraft must be merged for spacingand sequencing. The system issupplied with real-time trackingradar and flight plan informationfrom the air-traffic control facility’shost computer. The Airspace Tool(AT) is designed to achieve user

GLOBAL CIVIL AVIATION/␣ ␣ AFFORDABILITY

Radar tracks, Flight plans

Conflict resolutionadvisories

Clearanceinformation

Aircraft

Airspacetool

Sectortool

Fig. 1. Operational concept for user-preferred routing in en route airspace.

Fig. 2. Sample airspace with four sectors showing two typical conflictscenarios.

21G L O B A L C I V I L A V I A T I O N / A f f o r d a b i l i t y



efficiency for long time-horizon(15–25 minutes), generally inter-sector conflict-predictions bygenerating resolution advisoriesbased on minimum cost deviationfrom user-preferred routes. Reducedcontroller workload is also achievedthrough inter-sector conflict resolu-tion. The Sector Tool (ST) facilitatescontroller planning within a sectorfor short time-horizon conflict-prediction, trial plan (“what if”)solutions, and transition to theterminal area (see first figure).

The second figure shows asimple example of en route airspacewith four sectors and two sampleconflict scenarios. In both cases aminimum-cost resolution advisoryis computed by the AT. For the casein which the conflict is predictedacross sector boundaries, the ATpasses a suggested advisory to theappropriate sector. Each resolutionis checked by the sector controllerwith the aid of the ST, and, ifacceptable, is issued to the aircraftby the controller.

The Center-TRACON Automa-tion System software is being usedas a baseline for development,simulation, and field testing of theoperational concept.

Point of Contact: D. McNally(650) [email protected]

Conflict ProbabilityEstimation for Free FlightRussell A. Paielli, Heinz Erzberger

The Air Transport Associationestimates that the U.S. airlineindustry could save several billion

dollars annually in direct operatingcosts if the Federal Aviation Admin-istration (FAA) would relax routingrestrictions and adopt a policy of“free flight.” The safety and effi-ciency of free flight will benefit fromautomated conflict-prediction andresolution advisories to help air-traffic controllers maintain therequired separation between aircraftwhile minimizing the effect ontrajectories. Trajectory predictionis less certain the further in advancea prediction is made, however,so conflicts cannot be predictedexactly. A method is needed,

therefore, to estimate the probabilitythat a conflict will occur between agiven pair of aircraft. This conflict-probability estimate is important fordetermining both how and when tooptimally resolve conflicts.

An error model and an algo-rithm have been developed todetermine conflict probability. Basedon analysis of actual air-traffic data,the trajectory-prediction errors aremodeled as being normally distrib-uted (Gaussian), with the along-trackerror growing with prediction timeas a result of wind modeling error,as shown in the first figure. The two

Predictionerrorellipse

Minimumpredictedseparation

Pathcrossingangle

Prediction time

Predictedtrajectories

Predicted time

Fig. 1. Trajectory prediction error ellipses.


error covariances for an aircraft pairare combined into a single equiva-lent covariance of the relativeposition. The second figure showsthe combined error ellipse (based onthe combined covariance) centeredon one aircraft and the circularconflict zone centered on the other.The extended conflict zone is theprojection of the circular conflictzone in the direction of the relativevelocity. In two dimensions theconflict probability is the volumeunder the probability-densityfunction that is within that extended

conflict zone. In three dimensionsthe basic concept is similar but moredifficult to illustrate.

A coordinate transformationbased on the Cholesky decomposi-tion (“square-root” factorization) ofthe combined covariance is used toderive an analytical solution for theconflict probability. If the Gaussianerror model were exact, this solutionwould be exact for level flight and agood approximation for nonlevelflight. This analytical solution iscomputationally far more efficientthan an alternative solution based on

numerical integration. Efficiency isimportant because the algorithm isintended to run in real time. Thehigh efficiency also makes thealgorithm a convenient tool foranalyzing the effects of variousparameters.

The algorithm was programmedin C++ and successfully tested byMonte Carlo simulation over a widerange of encounter geometries. It hasalso been integrated into the Center/TRACON Automation System(CTAS). CTAS is a large softwaresystem developed at Ames ResearchCenter to help air-traffic controllersdo their job more efficiently andwith less stress. In this context, CTASpredicts the trajectories, determinesthe states of the aircraft at thepredicted point of minimum separa-tion, and sends that state informationto the conflict-probability algorithm.The probability results are then usedby CTAS to determine if a predictedconflict should be displayed to thecontroller. The system is currentlybeing tested on both live andrecorded air-traffic data that are sentto Ames on a dedicated line fromDenver Center.

Point of Contact: R. Paielli(650) [email protected]

Relative velocity

Extended conflict zone

Combinederror ellipse

Circularconflict zone

Fig. 2. Encounter geometry.




Conflict PredictionAlgorithms: Initial FieldTestDave McNally, Bob Vivona,Karl Bilimoria, Gerd Kanning,Steve Green, Ralph Bach,Allan McCrary, Ed Lewis

The Federal Aviation Adminis-tration (FAA) is responding to theneeds of the aviation community byexploring the concept of “free flight”for aircraft flying under instrumentflight rules. In free flight, en routeaircraft fly user-defined trajectories(defined by pilots or airlines) withonly minimal air-traffic control (ATC)adjustments to avoid restrictedairspace and loss of separation fromother aircraft. To facilitate user-preferred routing in all en routeenvironments, an extension of theground-based Center-TRACONAutomation System (CTAS) is beingdeveloped under the Advanced AirTransportation Technology programat Ames Research Center. The firststep is to add en route conflict-prediction capability to the CTASsoftware baseline. When fullydeveloped, en route conflict-prediction and resolution capabilityshould achieve many free-flightbenefits without significantly alteringcurrent ATC procedures or requiringmodification of airborne equipment.

An initial field test was con-ducted from September 24 throughOctober 8, 1996, at the Denver AirRoute Traffic Control Center (ARTCCor “Center”). The purpose was toconduct an initial evaluation of anen route conflict-prediction software,to evaluate an advanced trackerdeveloped by the BDM Corporation

and the FAA Host computer tracker,and to get an initial look at opera-tional issues pertaining to en routeconflict prediction. The Ames LearJet flew at angles of 0, 45, 90, 135,and 180 degrees with respect to jetroute J94 near Scotts Bluff (seefigure) to create (horizontal plane)conflicts with normal Center traffic,while maintaining normal safealtitude separation at all times. TheNASA Jet recorded differentialGlobal Positioning System (GPS)position and velocity data to evalu-ate the trackers. A version of CTASsoftware, modified for en routeconflict prediction, processed liveradar, flight plan, and wind data forall aircraft in the Denver Center.Predictions of minimum horizontalseparation between the NASAaircraft and each selected aircraftwere begun nominally 20 minutes

before the predicted time of mini-mum horizontal separation andcontinued just beyond minimumseparation.

A preliminary analysis of thedata shows that minimum horizontalseparation was predicted with1.5-mile accuracy during the15–25 minute period before thetime of actual minimum separation.This is well within the FAA separa-tion criteria of 5 miles for en routeairspace and 3 miles for the terminalarea. These results are based onhorizontal separation data related tothe distances between the NASA Jetand each of 59 other aircraft ofvarious types over 8 days of testflights.

Point of Contact: D. McNally(650) [email protected]

Scott Bluff

En routetraffic

Denver Centerboundary

En routetraffic

J94

NASALear Jet

Fig. 1. Flight profiles for initial field test of en route conflict prediction.


Assessing ControllerPerformance UnderSimulated Free-FlightConditionsRoger Remington, James Johnston,Eric Ruthruff, Maria Romera

Traditional air-traffic controlprocedures restrict air traffic todesignated routes and altitudes,analogous to highways in the sky.It is well understood that theseregulations, although promoting safeair travel, impose a price on theairlines in increased flight time andincreased fuel consumption. NASAis presently working with the FederalAviation Administration (FAA) todevelop plans to relax these con-straints on air traffic so that airlineswould be free to choose routes thatminimized delays and fuel costs.Free-flight refers to a family ofproposed concepts ranging from therelaxation of a few constraints tototal freedom of choice of flightpath.The goal of this joint NASA-FAAactivity, the Advanced Air Transpor-tation Technology program, is toensure that the relaxation of con-straints on airspace operations donot compromise safety. The Cogni-tion Laboratory at Ames ResearchCenter has been investigating theeffects that relaxing airspace con-straints can have on controllerperformance.

The extent to which constraintscan be relaxed and free flightenhanced is assumed to depend, inpart, on the workload of flightcrewand air-traffic control (ATC). Regard-less of how future responsibility is

Fig. 1. A traffic display. (a) With route restrictions. (b) Without routerestrictions.

(a)

(b)

divided between pilots and control-lers, the safety of the overall systemwill depend heavily on the ability ofcontrollers to perform their jobswell. One of the tasks of controllerswill be to look at situation displaysand understand the traffic, includingthe position and paths of the aircraft

displayed. Under the present systemthis kind of “situation awareness” isfacilitated by virtue of traffic patternsthat are orderly and have a familiarstructure. Research on humancognition suggests that reducing thestructure present in traffic flowsmight make it more difficult for




controllers to maintain situationawareness.

A series of experiments has beenconducted to determine empiricallywhether controller situation aware-ness is hindered by the loss of trafficconstraints under free flight. Tomeasure situation awareness, theexperiments tested the speed withwhich controllers could find con-flicts in traffic displays. The experi-mental design contained fourconditions: the status quo (both fixedroutes and fixed altitude restrictions),free flight (neither fixed routes norfixed altitude restrictions, fixedroutes only, or fixed altitude restric-tions only. Part (a) of the first figureshows a traffic display with routerestrictions; part (b) of the first figure

shows a traffic display with the samenumber of aircraft in which routerestrictions have been eliminated.In addition, the number of planesdisplayed was systematically varied.The second figure shows the resultsof one of the experiments in whichexperienced controllers detected thepresence of conflicts with the aid ofa computer conflict-assessment tool.The number of aircraft had strongeffects on performance; detectiontimes increased with increasednumber of planes in all conditions.Removing route restrictions did notnegatively affect performance, butremoving altitude restrictions didhave a modest negative effect.Similar results have been obtainedin conditions without computer-

assisted conflict detection. Theoverall results to date provide noreasons for pessimism about thefeasibility of considerable progresstoward the objective of free flight.

Point of Contact: R. Remington(650) [email protected]

Evaluating Cockpit Displayof Traffic InformationDisplays and RouteAssessment Tools for aFree Flight EnvironmentVernol Battiste, Walter W. Johnson

The Radio Technical Commis-sion for Aeronautics (RTCA) TaskForce 3 report on free flight recom-mends the immediate initiation of“the development of standards for acockpit situational awareness displayof traffic information.” In responseto these recommendations, theAdvanced Air TransportationTechnologies Program and the FlightManagement and Human FactorsDivision at Ames Research Centerhave initiated research on displaydesigns and formats to support flightdeck self-separation during free-flight operations.

The primary goals of this effortare to (1) conduct research tosupport the development of displayguidelines, and (2) evaluate anddesign cockpit display concepts andprototypes in support of cockpit-based separation during nominaland off-nominal operations fromdeparture to arrival including the enroute and transition phases of flight.

16 2012

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Fig. 2. Conflict detection time as a function of number of aircraft on screenfor the four restriction conditions.


Three critical areas have beenidentified in the display designresearch: (1) alerting; (2) situationalawareness; and (3) conflict resolu-tion. These three areas are interre-lated, and require an integratedapproach to arrive at good HumanCentered Design recommendations.

The research approach has beento identify attributes of displays thatare critical to crew alerting andconflict resolution, and also to applybasic and advanced principles ofgood display design. Two criticalattributes that have been identifiedare the surveillance data needed andthe format of the display. The mainprinciples guiding the CockpitDisplay of Traffic Information (CDTI)design effort are to minimize head-down time and dwell time, to reducescan frequency, and to improveinformation extraction. Anotherprinciple is minimizing the effect ofalerts by providing enough advancedwarning so pilots can have adequatetime to plan for potential problems.Finally, the design considers thatother cockpit duties prevent thecrew from focusing their full atten-tion on the task of self-separation.

Based on these principles andguidelines, an initial prototypeAirborne Management of En routeSeparation (AMES) display wasdesigned. To support the assessmentof alternative route planning, aRoute Assessment Tool (RAT) wasdesigned and incorporated into thedisplay design. The AMES displayprototype was integrated with theB-747 Navigation display and theRAT controls were located on thetop of the dash (see figure). Thedisplay was a two-dimensionaltrack-up god’s eye view of the trafficsituation that provided pilots with an

evolving four stage (threat-level)depiction of the traffic, based on theoutput of a collision alert systemdeveloped at the MassachusettsInstitute of Technology. In addition,this display allowed pilots to depictthe predicted location of traffic up to10 minutes in the future, and toassess the safety of pilot-proposedroute deviations.

The AMES display and RATwere evaluated by 10 Boeing 747

line pilots during a Crew VehicleSystems Research Facility B-747simulation of free-flight operations.During the simulation the AMESdisplay was compared with a morebasic display that had only one levelof alerting and no RAT tool. Thissimulation examined performanceduring eight en route traffic sce-narios incorporating multiple“traffic” aircraft, and one “intruder”

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aircraft on a conflict course, andused flight procedures based, in part,on FAA rules guiding separationduring VFR flight. The data from thesimulation show that pilots using theAMES display were able to maintaina significantly wider margin of safetybetween own-ship and intruder, anda lower overall level of conflictprobabilities between own-ship andintruder, and between own-ship andother context aircraft. The analysisalso showed no increase in theamount of maneuvering with theAMES compared with the basicdisplay, and in fact showed lessmaneuvering with the AMES displayunder some circumstances. Crewcomments on the display designwere all very favorable, and sug-gested that self-separation would bepossible if these types of displaysand tools were available on theflight deck.

Point of Contact: V. Battiste/W. Johnson(650) 604-3666/[email protected]@mail.arc.nasa.gov

Cockpit Displays forLow-Visibility TaxiingDavid Foyle, Elizabeth M. Wenzel,Durand R. Begault

These cockpit display projects(as part of NASA’s Terminal AreaProductivity (TAP) program) areaimed at developing candidatecockpit display and audio technol-ogy for the improvement of civiltransport (airline) taxi performancefor navigation and traffic avoidance,

when visibility is limited to 300 to700 feet by fog or rain.

Two display technologies wereinvestigated: a head-up display andan audio collision avoidance system.In the first, taxi guidance symbolsare shown on a head-up display(HUD). A HUD is a clear, glassdisplay mounted in the aircraft suchthat the pilot can see through it toview the out-the-window taxiway,and at the same time see informationthat is reflected on the display itself.This allows for display informationviewing while still maintaining out-the-window viewing.

The taxi symbology for theHUD is a subsystem of the TaxiwayNavigation and Situation Awareness(T-NASA) System. The other sub-systems are a perspective moving-map display, showing the plane’sposition at the airport, and three-dimensional (3-D) audio whichalerts to the direction of potentialtraffic incursions. For this project,superimposed HUD symbolsshowing current location andground speed, as well as pictorial

augmentations to the scene, havebeen developed (see first figure).The superimposed text symbols, the“Inner, Alpha/Bravo” format, repre-sents the current runway or taxiwaysegment (“Inner Taxiway”), the lastintersection passed (“Alpha”), andthe next intersection upcoming(“Bravo”).

The pictorial scene augmenta-tions include visual enhancementsthat aid the pilot in following thetaxiway clearance and completingturns. Using satellite positioning, thesymbology is projected virtually in3-D such that the symbols move andchange size in the same manner as ifthey actually existed in the out-the-window scene. We have termed this“scene-linked symbology.” Verticalcones on the side of the commandedtaxiway path depict the clearedroute on the HUD in superimposedsymbols. These are conformal andrepresent a virtual representation ofthe cleared taxi route on the HUD.The side cones and the centerlinemarkings are shown repeated every

Fig. 1. Scene-linked symbols (in white) superimposed on runway scene.


50 feet down the taxiway. Thevertical development and constantspacing should yield increasedcapability for estimating groundspeed, drift, and look-ahead capabil-ity for turns. Turn “countdown”warnings are shown in which eachturn has countdown (4, 3, and 2)centerline lights that are 300, 200,and 100 feet, respectively, beforeeach turn. This gives added distancecues for the turn. Virtual turn signs(with the arrows) give an added cuethat a turn is necessary. In addition,the angle of the arrow on the signrepresents the true angle of theturn (that is, 30 degrees right for a30-degree right turn). All of the HUDsymbols are scene-linked (virtuallyprojected as if they were real objectsin the world), allowing the pilot toprocess the symbology in parallelwith other traffic, including possibleincursions.

Simulation results have shownthat the taxi HUD symbology allowspilots to taxi faster in low-visibilityconditions and essentially eliminatesstraying off of the cleared groundtaxi route. These benefits have theadded bonus of also being associ-ated with decreased workload.

The second display technologyinvestigated was a 3-D audioGround Collision Avoidance System(GCAS) and navigation system—spatially localized auditory trafficand navigation alerts. Additionally,the Crew Roles and Proceduresproject is assessing the effect ofthese advanced technologies on thecockpit crew and controllers, as wellas recommending procedure modifi-cations as necessary.

Broadly stated, the TAP initiativeutilizes differential global position

sensing (DGPS) to track aircraft andother vehicles on the ground, andthen uses this information to providevisual and auditory situationalawareness by means of advancedguidance systems and displays.A 3-D auditory display is used as aground collision avoidance system(audio GCAS; see second figure)to provide immediate situationalawareness of crossing runways, ofpotential incursions, and of theaircraft being “off-track” (deviatingfrom centerline).

A full-mission simulation studywas run using 12 crews in aB-747-400 simulator. It was hypoth-esized that there would be a signifi-cant pilot preference for an audioGCAS system to be included on theflight deck. That preference for theaudio GCAS system was found. The

main conclusions of the study werethat an audio GCAS system wouldbe useful for avoiding potentialincursions under both normal andlow-visibility conditions, and that anauditory system presenting incursionalerts would be a useful adjunct toa moving-map display. A positivepreference was also found for thestereo headsets that were used toprovide the 3-D audio cueing.

Point of Contact: D. Foyle/E. Wenzel(650) 604-3053/[email protected]@mail.arc.nasa.gov

Fig. 2. Illustration of the 3-D audio GCAS display for the terminal-areaproductivity program.

3-D audio warning forblunder avoidanceunder RVR 300 conditions

GPS equippedobstacle(e.g., vehicle,other aircraft)

Pilot hearsvirtual audiowarning fromthe same angle

Criticaldistance

Angle ∆3-D audio fordirectionalizedwarning signal




Multi-Sensor ImageRegistrationMisha Pavel, Al Ahumada,Barbara Sweet

The use of various imagingsensors that can penetrate obscuringvisual phenomena (such as fog,snow and smoke) has been proposedto enable aircraft landings in low-visibility conditions. Images canbe obtained from both active andpassive sensors that are sensitiveto electromagnetic energy in thevisible, infrared, and millimeterwavelengths. Images can also beconstructed from database informa-tion, by rendering an image of thedatabase viewed from the estimatedposition of the aircraft. The focus ofthe current research effort is thedevelopment of image registration(superimposition) techniques insupport of this application.

Two challenges specific tomultisensor registration must beovercome. First, the features in twodifferent sensor images can be quitedifferent. For example, the contrastscan be reversed; the runway mightbe bright in a visible-light image anddark in an infrared image. Previouslyderived procedures for imageregistration rely on a high degree ofcommon features between the twoimages. However, for this applica-tion, there is no guarantee that thisexists; features apparent in onesensor might not be apparent in theother. Secondly, the two sensors areusually sited at different locations.This differential positioning canproduce distortions of the images

relative to each other which makeregistration more challenging.

A standard method of registeringtwo images is to find a spatialwarping of one image that mini-mizes the sum of the squareddifferences between the two images.However, for images from differentsensors, this does not work becausethe images are not the same whenthe warping is correct.

The figure shows results fromNASA’s new method. It estimatesthe image polarity relationshipseparately in local regions and dropsregions from the difference measurethat do not correlate well locally.The new method makes it possibleto find the correct spatial transforma-tion despite local differences infeature polarity and despite imagefeatures that are unique to a sensor.

Point of Contact: A. Ahumada/B. Sweet(650) 604-6257/[email protected]@mail.arc.nasa.gov

(a)␣ ␣ ␣ ␣ ␣ ␣ ␣ ␣ ␣ ␣ ␣ ␣ ␣ ␣ ␣ ␣ ␣ ␣ ␣ ␣ ␣ ␣ ␣ ␣ ␣ ␣ ␣ ␣ ␣ ␣ (b)␣ ␣ ␣ ␣ ␣ ␣ ␣ ␣ ␣ ␣ ␣ ␣ ␣ ␣ ␣ ␣ ␣ ␣ ␣ ␣ ␣ ␣ ␣ ␣ ␣ ␣ ␣ ␣ ␣ ␣ ␣ ␣ ␣ ␣ ␣ ␣ ␣ (c)

Fig. 1. Forward-looking infrared image (a), visible-light image (b), and theregistered image pair (c).

Flow Visualization of aFull-Scale Rotor in HoverBenton H. Lau, Alan J. Wadcock,Gloria K. Yamauchi

The rotorcraft industry hasstrongly recommended that wakegeometry and vortex strength bemeasured in addition to airloadsand acoustic measurements duringrotorcraft wind-tunnel tests. Theexisting aeroacoustic analysesrequire all three kinds of data forvalidation purposes, especially whenpredicting blade-vortex interaction(BVI) noise. Accounting for bladedeflection is also important inaccurately predicting BVI noise andin validating aeroelastic analyses. Inresponse to industry, Ames ResearchCenter initiated a test program toevaluate several flow-visualizationand blade-displacement measure-ment techniques for a full-scalerotor. Three techniques wereevaluated on an XV-15 tiltrotor inhover in the Ames 80- by 120-FootWind Tunnel.


Flow patterns on a rotatingblade can be visualized usingfluorescent microtufts. Thousandsof fluorescent microtufts wereinstalled on the upper surface of arotor blade. When illuminated bya powerful ultraviolet strobe, theblade motion was frozen and themicrotufts displayed the flowpattern. The microtuft images weresubsequently captured on film over a

range of thrust conditions includingrotor stall.

Rotor-wake geometry can bemeasured using laser-sheet and flowvisualization (see figure). A smokedispenser was installed near therotor tip, and an optics pod wasplaced below the rotor plane on thewind-tunnel floor. When fed with alaser beam via a fiber optic cable,the pod generated a thin laser sheet

and illuminated the entrained smokein the rotor wake. Images of therotor-wake geometry were recordedon video at several thrust conditions.In addition to testing the standardtiltrotor blades, a series of subwingswere tested and their effects on wakegeometry and tip-vortex roll-up wereevaluated.

Blade displacement was mea-sured using a stereo imaging tech-nique. Retro-reflective targets wereplaced along the blade span on theupper surface. Two asynchronousvideo cameras and strobes mountedin the wind-tunnel ceiling were usedto capture the frozen blade motion.The blade displacement or deforma-tion can be deduced from thepositions of these targets.

The success of these test tech-niques provides promising results forhover testing of a full-scale rotor.The test techniques can be appliedto forward flight testing.

Point of Contact: B. Lau(650) [email protected]

Skin-FrictionMeasurements on aHovering RotorAlan J. Wadcock, Gloria K. Yamauchi

A technique for acquiring skin-friction measurements on a fixedwing using a fringe-imaging skin-friction (FISF) technique was devel-oped at Ames Research Center inthe early 1990s. As long as the flowconditions are steady, as they are inhover, this technique can also beapplied to rotary wings. During a

Fig. 1. XV-15 tiltrotor and laser sheet setup in the 80- by 120-Foot WindTunnel at Ames.




hover test of a full-scale XV-15tiltrotor in the 80- by 120-Foot WindTunnel at Ames, the FISF techniquewas demonstrated for the first timeon a rotor.

The objective of this firstdemonstration was to determine thepracticality of the FISF techniquewhen applied to a full-scale rotor.Since the FISF technique had notbeen used previously in a rotating-flow environment, the effect ofcentrifugal force on the fringepatterns was a concern, as were thetransient effects caused by startingand stopping the rotor. The effect oftransients was minimized by remain-ing on the test condition for asuitable length of time. The effect ofcentrifugal force was shown to benegligible, once the oil-film thick-ness was reduced sufficiently.Chordwise skin-friction coefficientmeasurements were acquired at onelow-thrust condition at three bladeradial stations. Measurements on theXV-15 tiltrotor blade at a radial

station of r/R = 0.24 are shown inthe accompanying figure for a tipMach number of 0.59, a thrustcoefficient of 0.0035, and aReynolds number of 1.1 million.The measurements clearly indicatethe location of the transition fromlaminar to turbulent flow.

Point of Contact: A. Wadcock(650) [email protected]

Rotor Data CorrelationRandall Peterson

The use of wind-tunnel testmeasurements, flight-test measure-ments, and analytical predictionsplays a key role in the developmentof new rotor systems. Such tests aretypically performed by using a rangeof rotor-system sizes and wind-tunnel test facilities. To ensure theaccuracy of wind-tunnel testing

methods, an experimental validationstudy was conducted using testresults from model- and full-scaletests to compare with flight-test data.

Accurate measurements ofrotorcraft performance as measuredin a wind tunnel are strongly influ-enced by the test-section configura-tion, that is, whether it is a closed oropen jet. The influence of wind-tunnel walls on the induced velocityof lifting bodies has been studied bymany researchers over the years.Methods have been developed toadjust the angle of attack anddynamic pressure for fixed-wingaircraft in wind tunnels to approxi-mate free-flight conditions. Thesemethods have largely been adoptedby the rotorcraft community withvery little testing to verify theirapplicability to helicopter rotorsand flight-test measurements.

Tests conducted by theDeutsche Forschungsanstalt fürLuft- und Raumfahrt e.V. (DLR) inthe Duits-Nederlandse Wind Tunnel(DNW), under the auspices of theU.S. Army/German Memorandumof Understanding on CooperativeResearch in the Field of HelicopterAeromechanics, have provided datasuitable for evaluating these meth-ods. A 40% scale-model BO-105rotor was tested in five differentwind-tunnel test sections: (1) 6- by6-m closed, (2) 8- by 6-m closed,(3)␣ 8- by 6-m open slots, (4) 9.5- by9.5-m closed, and (5) the 8- by 6-mopen jet. These data along with full-scale data from an Ames 40- by80-Foot Wind Tunnel test and aDLR flight-test program provided ameans to evaluate wind-tunnel wall-correction methods specifically forhelicopter rotors. Good correlation

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of rotor power over a range ofadvance ratios for these threedatasets was shown using wall-correction methods after accountingfor trim differences between thedatasets.

Recent rotor-data correlationwork has focused on the ability ofanalytical prediction methods suchas CAMRAD/JA (ComprehensiveAnalytical Model of RotorcraftAerodynamics and Dynamics,Johnson Aeronautics) to accuratelypredict rotorcraft performance. Full-scale BO-105 rotor-system dataacquired in the Ames 40- by 80-FootWind Tunnel are being used in thisanalytical study. From previousexperimental comparisons, it wasshown that the rotor-performancemeasurements were strongly

influenced by the presence of thewind-tunnel walls. Using the wall-correction method of Glauert, theangle of attack of the rotor system inthe tunnel was corrected and used inthe trim conditions of the CAMRAD/JA analysis. As shown in the figure,the accuracy of predicted rotorpower is significantly improvedwhen the angle-of-attack correctionof Glauert is applied to the trimconditions of the rotor in theanalysis. The analytical predictionsof rotor power as a function of rotorthrust using a free-wake analysisare shown.

Point of Contact: R. Peterson(650) [email protected]

Canard Rotor/WingHover TestStephen Swanson, John Madden

In a joint program betweenNASA and McDonnell DouglasHelicopter Systems, a one-half-scalerotor model of the McDonnellDouglas Canard Rotor/Wing (CRW)rotorcraft was tested in the 80- by120-Foot Wind Tunnel at AmesResearch Center. This test wasconducted to evaluate the hoverperformance of the unique elliptical-airfoil rotor being planned for theCRW. The CRW is a stoppable-rotordesign which can hover and fly atlow-speeds like a conventionalhelicopter, whereas in its stopped-rotor mode it can fly at high speedscomparable to those of fixed-wingaircraft. Initial concepts include aland- or ship-based medium-rangevertical takeoff and landing,remotely piloted vehicle.

A two-bladed teetering rotor isused to generate the required lift forhover and low-speed forward flight.Once the rotorcraft is at a sufficientforward velocity, the required liftgeneration is transferred from therotor to a canard and horizontal tail.What is unique about this rotor isthat it is driven by high-pressureair exhausted at the rotor tips asopposed to the conventional heli-copter in which the rotor is shaft-driven. In the flight vehicle,conventional turbofan engines areused to supply the high-pressure airto the rotor. Because the CRW’srotor is stopped to allow high-speedforward flight, the rotor’s airfoil crosssection must be elliptical. This is acompromise between the optimum

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Fig. 1. Rotor power with and without angle-of-attack correction applied tothe trim conditions of the rotor in the analysis.




airfoil shape for conventional rotorflight and that for high-speedstopped-rotor flight.

The fixed-wing aerodynamiccharacteristics of the completeaircraft were evaluated in earliertests. In this recent test, the isolatedrotor was evaluated in hover in theAmes 80- by 120-Foot Wind Tunnel;that tunnel was used because it hasthe unique capability to provideheated, high-pressure air that couldbe used to simulate the exhaust

gases of the CRW’s engine. Thefigure shows the isolated rotorinstalled in the test section andconnected to the high-pressure airsystem. Preliminary results indicatethat the rotor was capable of gener-ating the required lift for takeoff andhovering flight. Comparisons withpredicted aerodynamic performanceshowed that the actual thrustgenerated was greater than predictedfor the same power input. On theother hand, comparisons of the

actual and predicted internalpressure measurements indicatedhigher than expected duct losseswithin the rotor internal piping.

Point of Contact: S. Swanson(650) [email protected]

Fig. 1. Isolated rotor model installed in the Ames 80- by 120-Foot Wind Tunnel.


In-flight Dynamic StallResearchRobert Kufeld, William Bousman

The objective of this work is toimprove the complex dynamic-stallaerodynamic models of a helicopterrotor in high-speed, high-loadconditions. The improvement ofthese models should serve to reducethe design and development costof new helicopters, because thedynamic-stall condition is thedriving force in determining thestrength of the helicopter controlsystem. Test conditions were identi-fied and studied from the flight-maneuver data collected during theUH-60A Airloads Program, whichprovides information about the

dynamic-stall phenomena. UH-60Aairloads data are available to NASA’scustomers for similar studies throughan electronic database and searchengine called “TRENDS,” which ismaintained at Ames ResearchCenter.

The figure shows some of thecomplex loading a helicopter rotoris subjected to during a high-speedturn. The data show the measuredpitching-moment calculation derivedfrom pressure transducers locatedat radial station r/R = 0.92, at anadvance ratio of 0.39 and a loadfactor of 1.5. The figure clearlyshows the five rapid and largenegative pitching-moment depar-tures the blade experiences as itmakes one revolution during this

test condition. The two pitching-moment departures near 280 and355 degrees have been clearlyidentified as dynamic-stall events.The two pitching-moment departuresnear 95 and 135 degrees have beenlinked to passage of shock wavesover the airfoil; the final pitching-moment departure near 50 degreesappears to be caused by a combina-tion of two effects: supersonicaerodynamic and dynamic-stallvortex shedding. These data showthe need for dynamic-stall modelimprovement at both the traditionallow-speed range of the fourthquadrant and the unexpected high-speed range found in the firstquadrant of the rotor.

Point of Contact: R. Kufeld(650) [email protected]

Stall Control of HelicopterRotorsKhanh Q. Nguyen

A control system based onblade-pitch actuation was developedto suppress stall on helicopter rotors.Stall suppression would allow thehelicopter flight envelope to beexpanded and would alleviate stall-induced loads and vibration. Thecontrol system was implementedin a comprehensive rotorcraftanalysis, which was based on afinite-element method and whichincluded unsteady aerodynamiceffects (dynamic stall) and nonuni-form inflow models. The stall-suppression system is based on atransfer-matrix approach; it employs

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Fig. 1. Section moment versus rotor azimuth for r/R = 0.920 in a high-speedturn; advance ratio = 0.390 and load factor = 1.50.




In general, however, stallsuppression did not guaranteeperformance improvements. Theresults also showed the distinctionbetween stall suppression andperformance improvement withactive control. When the controlleraimed to reduce the shaft torque,rotor-performance improvementcould be achieved, but with a smalldegradation in stall behavior.

Point of Contact: K. Nguyen(650) [email protected]

Apache AH-64D FlightTest PredictionsEarl P. N. Duque

Recent design changes to theAH-64D (Apache) helicopter havecreated unfavorable handlingqualities that may be caused bychanges in the aerodynamic flowfield. Engineers at McDonnellDouglas Helicopter Systems neededto quickly understand the flowcharacteristics and to evaluatepotential ways to alleviate theproblem. Computational fluiddynamics (CFD) is an ideal tool forexamining the effect of late-cycledesign changes because it is muchfaster and cheaper than flight testing.

The objective of this project wasto use CFD methods to study theflow field around the helicopter in itscurrent configuration and then withseveral variations which designersproposed to improve the handlingqualities. The simulation results hadto be obtained quickly in order to

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Fig. 1. Stall regions over rotor disk without the stall-suppression system (a)and with the system (b).

a stall index as a measure of stall.The results showed that stall couldeffectively be suppressed usinghigher harmonic control at bothcruise and high-speed flight condi-tions. The effectiveness of the stall-suppression system is shown in the

figure in which the stall regions areshown without the system (part (a))and with the system (part (b)) at ahigh-thrust, high-speed flight condi-tion. The control amplitude wassmall, less than 1 degree.


decide which designs would be builtand tested in flight.

Inviscid simulations were donewith the TIGER code by John Meltonof Ames Research Center (ARC). Itsunstructured Cartesian formulationlargely bypasses the time-consumingand tedious task of grid generation,allowing for fast turnaround of verycomplicated models. Results fromthe initial geometry (see figure (seeColor Plate 3 in the Appendix))influenced two of the proposeddesign solutions. Subsequent studyof five new designs showed that onedid not warrant further investigation.Since the validity of an inviscidapproximation is questionable in acomplex, vortex-dominated flow,intensive study of a geometricallysimplified model (the isolatedfuselage without engine, wing, ortail surfaces) using the thin-layerNavier-Stokes equations was con-ducted using the OVERFLOW codeby Pieter Buning of ARC. Thesesimulations gave further credenceto the baseline inviscid computa-tions. The combination of complex-geometry/simplified-physicssimulations with simplified-geometry/complex-physics simula-tions provided McDonnell Douglas’sengineers with an overall under-standing of the Apache flow fieldand with quick feedback on pro-posed design changes.

Point of Contact: E. Duque(650) [email protected]

Rotor-Wake/FuselageInteractionPaul M. Stremel

The interaction of the wakegenerated by a rotor with thefuselage of the vehicle has profoundeffects on the overall efficiency ofthe vehicle. These effects have beenclearly demonstrated in flight asvehicle vibration and download.Although they are clearly demon-strable in flight, the quantitativeaspects of the interactions are notclearly understood. Numerousnumerical and experimental investi-gations have been conducted inefforts to better understand the rotor-wake/fuselage interaction. However,each of these investigations concen-trated on a unique rotor/geometrycombination for which conclusionscan be drawn only for that particularconfiguration. A generalized methodfor optimizing rotor performanceand minimizing fuselage interactionis not forthcoming. As a result,numerical methods must be appliedto each configuration to betteridentify the aerodynamic effectsof the rotor/fuselage interaction.

The present research wasconducted to obtain baselineinteraction results—aerodynamicand acoustics data—for the flowsurrounding the Tilt Rotor Aero-acoustic Model (TRAM) isolated-rotor configuration. It is extremelyimportant to minimize the interac-tion of the support hardware withthe rotor to insure quality data.However, because of geometriclimitations of the support hardware,tunnel installation, and test enve-lope, a perfectly isolated rotorcannot be tested. The numerical

method used to model the TRAMisolated-rotor configuration is acombination of the OVERFLOWcomputational fluid dynamics codeand the PEGSUS domain connectiv-ity program. The isolated-rotorconfiguration consists of a rotor anda motor/gearbox assembly. In thecurrent investigation, the rotor isrepresented by an actuator-diskmodel. Results were computed forCT = 0.14 at angles of incidence of0 and 15 degrees. The results areshown in the first figure (see ColorPlate 4 in the Appendix) for 0-degreeincidence and in the second figure(see Color Plate 5 in the Appendix)for 15-degree incidence. Shown ineach figure are the vertical velocitycontours and the flow-field stream-lines. The vertical velocity contoursare shown at the rotor plane and ata station on the model support. Incomparing the streamline results, therotor wake for the 0-degree angle ofincidence directly interacts with themotor assembly. However, at the15-degree angle of incidence therotor wake is completely clear of themotor assembly. In comparing thevelocity contours at the rotor plane,the contours indicate an interactionover the motor assembly for the0-degree angle of incidence butconsiderably less interaction at the15-degree angle.

Point of Contact: P. Stremel(650) [email protected]




Navier-Stokes Simulationof High-Lift AerodynamicsKarlin Roth, Stuart Rogers

The use of the methods ofcomputational fluid dynamics (CFD)in order to understand the flow overhigh-lift wings configured for takeoffand landing with leading-edge slatsand slotted trailing-edge flaps willcontribute to the design of simpler ormore efficient high-lift systems forsubsonic transport aircraft. The long-range objectives of this work are todevelop an accurate and efficientNavier-Stokes analysis method forflow over the high-lift systems ofsubsonic transport aircraft and toexamine critical physics affectinghigh-lift system design. The particu-

lar near-term objective is to predictthe flow about a subsonic transportconfigured for high lift and to assesswind-tunnel interference effects onthe flow about this test article.

The OVERFLOW code wasused to investigate the flow about asubsonic transport configuration.The simulations are steady-state,employ the Spalart-Allmaras turbu-lence model, and utilize multigridconvergence improvement schemes.The structured, overset grid systemwhich discretizes the fuselage, high-lift wing elements, and nacellesconsists of 16 million points within36 zones (see figure). During FY96,surface grids were generated fromthe computer-aided design defini-tion; volume grid methods including

element edge grids, wake place-ment, and wake smoothing strategieswere developed, verified, andapplied. Importantly, the simulationteam demonstrated first-of-a-kindcomputations in utilizing a viscousCFD analysis for a complex three-dimensional high-lift configuration.The solution matrix includes a totalof 18 cases which document theflow for a range of angles of attack,with and without powered engines,and in free-air and within the12-Foot Pressure Wind Tunnel atAmes Research Center.

Comparison of the free-air andwind-tunnel simulations showssignificant wall-interference effectswhich vary with the model attitude.In general, simulations conducted inthe wind tunnel exhibit earlier stallthan do the free-air calculations.Further, in addition to an earlier stallangle, powered simulations in thewind tunnel attain lift values nearstall which are about 8% higher thanthe free-air values. In order to testthe Wall Interference CorrectionSystem developed for the 12-FootPressure Wind Tunnel on a pow-ered, high-lift model, it was appliedto the simulated data at selectedconditions. The initial analysisindicates that this correction methodmay not be appropriate at conditionsnear maximum lift.

Point of Contact: K. Roth/S. Rogers(650) 604-6678/[email protected]@mail.arc.nasa.gov

Fig. 1. Overset grid system within cross section of a multielementhigh-lift wing.


Lift-Jet Effects onPowered-Lift STOVLModelKarlin Roth

During the transition from hoverto wingborne flight, short takeoff andvertical landing (STOVL) aircraft relyon the direct thrust of lift jets tosupplement aerodynamic wing lift.The jets usually induce a loss of liftand a change in the nose-up pitch-ing moment on the vehicle; both ofthese effects increase with increasingforward velocity. Thus, properdesign of STOVL aircraft requiresan understanding of the physics ofthe lift-jet/airframe interaction.

The ability of three-dimensional,laminar and turbulent Navier-Stokescomputations to simulate theperformance of a geometricallysimplified STOVL model duringtransition flight was investigated.Simulations were made using theOVERFLOW code for the modelwhich consists of a 60-degreecropped delta wing planform; asimple fuselage shape blended to thewing; and tandem, circular, high-pressure-air lift jets that exit perpen-dicularly to the flat lower surface.Predictions were compared withmeasurements at a free-stream Machnumber of 0.146, a 10-degree angleof attack, and with sonic lift jets.Flow visualization shows thestructure of the wing leading-edgevortices and the lift jets; the deflec-tion of the lift jets is illustrated in thefigure using Mach number contoursin the model’s symmetry plane.

Although grid refinementsimprove the computational results,none of the computations com-pletely characterize the wing

leading-edge flow field or the flowwithin 2 diameters of the jet exits.For laminar calculations, the pres-sure suction peaks at the wingleading edge tend to be initiatedfarther inboard, to cover more areaon the wing, to have slightly lesssuction, and to agree better with themeasurements than the turbulentpredictions. Notably, the simulationspredict a jet-induced lift loss forthe model that is mostly due todecreased suction at the wingleading edge.

Point of Contact: K. Roth(650) [email protected]

Vortex Core Detectionfor Computational GridRefinementDavid Kenwright

Predicting rotor wake is one ofthe most challenging problems inrotorcraft computational fluiddynamics (CFD). The rotor wake isthe disturbed flow that is left behindas the rotor blade cuts through theair. The wake rolls up into vorticesnear the blade tips, a result of thepressure differences caused by themoving rotor. These vortices, anunwanted side effect of lift, causecontrol buffeting, airframe vibration,and noise. The requirement for lownoise is particularly important for

Fig. 1. Mach number contours taken in the symmetry plane to illustrate thedeflection of lift jets.




civilian helicopters and tiltrotorswhich operate in highly populatedareas.

A major problem with the CFDsimulation of rotorcraft is that the tipvortices diffuse too quickly becauseof inadequate grid resolution.Adaptive grid-refinement schemesdeveloped at Ames Research Centerhave been partially successful incapturing these vortices, althoughinadequate grid resolution near thevortex core causes discrepanciesbetween computed and wind-tunnelresults.

A vortex-core detection tech-nique was implemented in theUnsteady Flow Analysis Toolkit(UFAT) to permit scientists to locateand visualize the regions of swirlingor rotating flow. This technique isbased on an eigenvector methoddeveloped at the MassachusettsInstitute of Technology with fundingfrom Ames. The figure (see ColorPlate 6 in the Appendix) showsvortex cores extracted from asimulation of a helicopter rotor inforward flight. The vortex cores (redlines) become disjointed where thecomputational grid is too coarse. Inthis simulation, the grid was refinedbased on the vorticity magnitude.From the visualization, it is apparentthat the grid refinement processfailed to capture the vortex core.

The vortex cores are extracted ina batch computation which can takefrom seconds to hours to completedepending on the size of the datasetand the complexity of the flow. Forthe rotorcraft simulation shown inthe figure which consisted of800,000 tetrahedral elements, theextraction process took less than8 seconds on a Silicon Graphics

Power Onyx workstation. The sametechnique has also been applied tomuch larger, unsteady simulations ofaircraft to reveal the time-evolutionof vortex cores.

Point of Contact: D. Kenwright(650) [email protected]

Wingtip Vortex FlowsJennifer Dacles-Mariani,Dochan Kwak

The wingtip vortex flow hasbeen the subject of numerousstudies. Its significance has beenseen in practical problems such aslanding separation distances foraircraft, blade-vortex interaction,and cavitation on ship propellerblades (see first figure). Despite thesenumerous studies, most of the wake-vortex flow behavior is still notclearly understood.

This work is part of an ongoingcomputational study of the tip-vortexflow through initial formation/roll-up, growth, and decay. In thisparticular study, the near- andintermediate-fields behind the wingsare investigated to (1) explore amore physical modeling of the flowby including the viscous upstreameffects; (2) provide an improvedvortex flow field to be used as inflowfor the intermediate-wake; and(3) investigate the validity andapplicability of a simplified Navier-Stokes solver using the velocity/vorticity formulation in tip-vortexflow prediction.

The approach taken is to derivea wake model from the full Navier-Stokes equations using the velocity/vorticity formulation. It has theadvantage of being able to retainsome of the flow physics without alot of empiricism. These equationsallow physical diffusion in thestreamwise direction, includingviscous upstream effects and vortex

Fig. 1. Schematic of a downstream wake of an aircraft.

UpwashDownwash


stretching. For vortex-dominatedflows, vorticity is the natural choiceof variable. The accuracy of themethod may be better preservedsince it is being calculated directly.

From this study, a detailedaccount of tip-vortex formation andof the roll-up process was accom-plished. The roles of numerics andturbulence models in tip-vortexprediction was also studied in detail.The preliminary results indicatedthat the velocity/vorticity formulationusing the preconditioned conjugategradient method was successful inpredicting wake-vortex flow. Com-parison with measured data of a0.03 scale model of the Boeing 747aircraft, taken in the 80- by 120-Foot

Wind Tunnel at Ames ResearchCenter showed a similar trendbetween the measured and thecomputed upwash and downwashvelocities (see second figure). Theslopes of the velocity across thevortex were predicted well by thecomputation. Most of the disagree-ment is in the region where thesampling period of the measureddata was not long enough, whichresulted in the irregularity ofthe data.

Point of Contact: J. Dacles-Mariani(650) [email protected]

Transonic OversetPotential SolverTerry Holst

The “full-potential+boundary-layer” approach for transonic cruiseanalysis and design can be up to100 times faster than Navier-Stokesapproaches and just as applicableover a wide range of cases involvingweak shock waves with little or noboundary-layer separation. A fastfull-potential capability using azonal grid approach for generalgeometry modeling will be a valu-able tool for near real-time assess-ment of aerodynamic shapes in thedesign or wind-tunnel environments.

The objective of the presentwork is to develop a full-potentialanalysis and design capabilityutilizing the Chimera zonal gridapproach that will be compatiblewith the well-establishedOVERFLOW Euler/Navier-Stokesflow solver. Such an approachwould be extremely cost effective,especially considering that all ofthese approaches would utilize thesame problem setup and post-processing software, and to a largeextent, the same grid-generationsoftware.

A transonic three-zone wing-fuselage solver (for inviscid flow)has been developed and validatedusing experimental pressure mea-surements (see figure). This half-million-grid-point computation,which includes surface definition,surface-grid generation, volume-gridgeneration, Chimera hole-cutting,donor-cell search, flow-field genera-tion, and PLOT3D file generation,required about 1 minute of computer

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Fig. 2. Upwash and downwash velocity profile at x/c = 162 feet.




time on a single processor Cray C90computer.

In developing this solver, a new,approximate Chimera donor-cellsearch algorithm has been devel-oped that is up to 100 times fasterthan previous techniques. Forexample, in two-zone cases, thenew algorithm can find donor cellsat a rate in excess of 60,000 cellsper second on a single processorCray C90 computer. This searchalgorithm has an approximatecharacteristic that will automaticallyutilize a nearest-neighbor cell whenthe actual donor cell cannot befound, thus reducing the chance fororphan points to exist.

Point of Contact: T. Holst(650) [email protected]

Real-Time Particle Tracingin Time-Varying FlowsDavid Kenwright, David Kao

Particle tracing is a scientificvisualization technique that iswidely used to study aeronauticalsimulations. In time-varying flows,particle tracing can be used toproduce streaklines (a visualizationtechnique commonly used in wind-tunnel experiments) by simulatingthe continuous injection of particlesinto a flow. To detect important flowfeatures, several thousand particlesmust be injected and traced througha flow field by using numericalintegration, which makes particletracing computationally intensive.Consequently, streaklines are usuallypre-computed in a batch process

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Fig. 1. Wing/fuselage surface-pressure comparisons RAE wing-fuselage,M∞ = 0.8, α = 2°. (a) Upper wing; (b) upper fuselage.

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by using programs, such as theUnsteady Flow Analysis Toolkit,and then playing them back later inanimations or videos—a processwhich can take hours.

A real-time algorithm forcomputing and displaying streaklinesknown as the tetrahedra method,was developed by members of thevisualization technologies groupat Ames Research Center. Theimproved performance offered bythe tetrahedra method now allowsstreaklines to be computed andvisualized in real time on high-endSilicon Graphics, Inc. workstations.The benefit to scientists is immediatevisualization of their data and thecapability to interactively exploretime-varying flows. Comparisonswith conventional particle-tracingalgorithms have verified that thetetrahedra method is accurate aswell as fast.

The tetrahedra method has beeninstalled in two visualization systemsdeveloped at Ames: the VirtualWindtunnel (see the figure (seeColor Plate 7 in the Appendix)) andthe Unsteady Flow Analysis Toolkit.

Point of Contact: D. Kenwright(650) [email protected]

NASA MetacenterMary Hultquist

The NASA Metacenter is anexploratory project of the ParallelSystems Groups at Ames ResearchCenter and Langley Research Center.The focus of the project is to achievemore effective use of NASA super-computers by making the systems

more readily available to research-ers, and by providing quickerturnaround for batch jobs, a largerrange of available resources forcomputation, and better distributionof the computational workloadacross multiple supercomputers.

The current homogeneousconfiguration of the Metacenter linksthe IBM SP2 computers at Ames andthose at Langley. With the systemssimilarly configured, each Centercan rely on help from the other fortroubleshooting difficult problems.Planning and problems are discussedat weekly teleconferences, andproblems are resolved more quicklybecause the experience of personnelat both sites is utilized.

The implementation of theMetacenter includes a “peer sched-uler” to interact with the PortableBatch System (PBS) queuing systemused on each system. In this model,as long as all systems have work todo, they act as independent comput-ers. But when the utilization of onesystem drops below a predefinedutilization threshold, then peerscheduling begins. A system thatis short of jobs, “asks” the othersystems in the Metacenter (its“peers”) for a list of all the queuedjobs on the remote systems. It thengoes through a series of checks,verifying that it can indeed run aspecific job. If all the tests arepassed, the scheduler requests the

Apr 6

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Fig. 1. FY96 utilization on the IBM SP2.




PBS to move the job to the localserver. The job is then run locally,and the results sent back to the user.

This implementation hasresulted in a more balanced utiliza-tion of the Metacenter systems, asshown in the figure. The users arethus able to get jobs returned morequickly, because a job does notwait in a queue at one system whileanother system sits idle. Moreover,system downtime is decreasedbecause personnel at both sites canwork together to get down systemsback into production.

Point of Contact: M. Hultquist(650) [email protected]

Portable Batch SystemDavid Tweten

As of this year, all super-computers at Ames Research Center,whether production or testbed, andregardless of manufacture, run thesame batch and cluster controlsystem, the Portable Batch System(PBS). Most recently, Ames’s twoCray C-90s, called the vonNeumannand Eagle, as well as the Center’sCray J-90 cluster, called the Newton,were converted to use the PBS astheir sole production batch system.The PBS is a research batch process-ing and cluster control softwarepackage written at the Center.

VonNeumann is NASA’s largestsupercomputer; it is used to performcutting-edge research for NASA’saeronautics-focused programs andfor base research and technology.

Eagle is the production super-computer for general science andengineering research for the Officeof Aeronautics and Space Transpor-tation Technology. Newton is atestbed supercomputer cluster,intended to ease migration ofcomputer codes between vectorcomputing and distributed-computing paradigms. The PBSallows construction of customschedulers using any of threedifferent languages. It is a keycomponent in NASA’s plan todevelop metacenters, virtual com-puter centers composed of machinespotentially supplied from severalvendors, and potentially sited inseveral locations.

The PBS beta program endedthe fiscal year with 51 client sites,distributed among government,universities, and private industry.

Point of Contact: D. Tweten(650) [email protected]

Developing a ClusterComputer fromWorkstationsReese L. Sorenson

Finding adequate computationalresources to meet the ever-expandingneeds of aerodynamic simulation bycomputational fluid dynamics (CFD)has always been a challenge, oneexacerbated by recent budgetaryconstraints and redirected priorities.Facing a possible decrease ofavailable computer time in the face

of growing needs, it is important thata new source of computing powerbe found for researchers at AmesResearch Center.

It was realized that in terms ofraw computer power the SiliconGraphics, Inc. (SGI) workstationssitting on the researchers’ desks,considered together, had powerapproximately equal to that of afour-processor CRAY C-90. Sincethis resource was sitting idle everynight and most weekends, a projectwas undertaken to link these work-stations, thus creating a clustercomputer.

Two needs had to be met tomake this a reality. One was for fastinterprocessor communication. AGrand Junction fast Ethernet dataswitch was obtained, and the24␣ most powerful of the approxi-mately 60 workstations in use wereinstalled on the data switch. It isexpected that this switch will at leastdouble the interprocessor communi-cation speed for these workstationsby eliminating “data collisions” at alocal network router.

The second need was forscheduling software to queue jobs,oversee their execution, and gener-ally make the workstations functiontogether as a computer. The PortableBatch System (PBS) software,developed locally at Ames andalready functioning as the operatingsystem on a CRAY supercomputerand on a dedicated workstationcluster, was ported to thesemachines and customized for thisimplementation.

The cluster is scheduled to beavailable 12 hours per day through-out the year. Test cases have beenrun successfully on it. Recently


acquired workstations, even morepowerful than those originally used,are being installed in the cluster.Documentation to be posted on theWorld Wide Web has been written.

The significance of this projectis twofold: first, the critically impor-tant work of aerodynamic simulationat Ames will continue to haveadequate computational resources;second, the software techniques andthe experience of this project areavailable to others facing similarconstraints.

Point of Contact: R. Sorenson(650) [email protected]

Planar DopplerVelocimetry UsingPulsed LasersRobert L. McKenzie

Recently, planar dopplervelocimetry (PDV) has been shownby several laboratories to offer anattractive means for measuring three-dimensional velocity vectors every-where in a light sheet placed in aflow. Unlike other optical means ofmeasuring flow velocities, PDV isparticularly attractive for use in largewind tunnels where distances to thesample region may be severalmeters, because it does not requirethe spatial resolution and tracking ofindividual scattering-particles or thealignment of crossed beams at largedistances. To date, demonstrationsof PDV (called “doppler globalvelocimetry” by some authors) havebeen made either in low-speed flows

without quantitative comparisonwith other measurements, or insupersonic flows where the Dopplershift is large and its measurement isrelatively insensitive to instrumentalerrors. Moreover, most reportedapplications have relied on the useof continuous-wave lasers, whichlimit the measurement to time-averaged velocity fields.

The objective of this study hasbeen to quantitatively determine thelimits of PDV capabilities for appli-cations in large-scale wind tunnelsthat are intended primarily forproduction testing of subsonicaircraft. For such applications, theadequate resolution of low-speedflow fields requires accurate mea-surements of small Doppler shiftsthat are obtained at distances ofseveral meters from the sampleregion. In addition, the use ofpulsed lasers provides the uniquecapability to obtain not only time-averaged fields, but also theirstatistical fluctuation amplitudes andthe spatial excursions of unsteadyflow regions such as wakes andseparations.

To accomplish the objectives,the PDV measurement process wasfirst modeled and its performanceevaluated computationally. Thenoise sources considered includedthose related to the optical andelectronic properties of charge-coupled device (CCD) arrays andto speckle effects associated withcoherent illumination from pulsedlasers. The signal-noise estimateswere incorporated into the PDVsignal analysis process and com-bined with a spectroscopic modelof the iodine vapor cell used todiscriminate Doppler frequency

shifts and with computed scatteringsignals using a Mie scattering theoryfor polydisperse smoke particles. Therelevant parameters incorporated arange of practical aerodynamic testconditions and facility sizes. Theresults (1) helped define the opti-mum values of the instrumentparameters, (2) showed that theexpected signal levels from apractical PDV system were suffi-ciently large to allow its usefulapplication in large facilities, and(3) showed that the expectedvelocity measurement uncertaintieswere small relative to the meanvelocities of interest for most sub-sonic, large-scale wind-tunneltesting.

PDV performance was thendemonstrated by using severalbench-top setups, including arotating wheel where the exactvelocity field was always knowneverywhere, a turbulent air jet withflow properties that were calibratedusing pitot and hot-wire probes,and stationary solid and aerosoltargets where only the PDV noise isobserved. Images from these targetswere used to validate the modeldescription of noise magnitudes andto confirm the minimum velocitiesthat could be resolved. The bench-top experiments also allowed theoptical configuration and calibrationprocedures of the instrument to bedeveloped into a robust and easilyoperated system that is applicable tothe environment of large-scale windtunnels. An example of some resultsis shown in the figure (see ColorPlate 8 in the Appendix) where theaverage axial velocity field and itsroot-mean-square fluctuationamplitudes are displayed for the flowin a low-speed, turbulent, free jet.




The plane of the image is normal tothe jet centerline. The velocityprofiles are taken along the grid linesshown in each image. The velocityfield, part (a) in the figure, shows theaverage velocity distribution of thecore flow and the fluctuation field;part (b) of the figure shows the highrelative fluctuation amplitudes in theturbulent shear layer at the edge ofthe jet. These measurements weremade with a preliminary PDVoptical system that was capable ofdetermining only one velocitycomponent. The combined use oftwo additional systems would allowthe determination of all threevelocity components simultaneouslyfrom each laser pulse.

The PDV measurement capabili-ties developed in this study demon-strate that PDV offers significantadvantages when compared withother means of measuring velocityfields in large-scale, subsonic windtunnels. Measurements obtainedfrom each laser pulse allow theaccurate resolution of completevelocity vector fields with resolu-tions of instantaneous speeds as lowas 2 m/sec. Much smaller averagespeeds can also be resolved. Fromthe pulse-to-pulse data, both meanvelocities and their fluctuationamplitudes can be determined inany aerosol-seeded flow withadequate optical access, includingcomplex, three-dimensional, turbu-lent flows. The method has no upperlimit above which velocity can notbe measured, other than in extremehypersonic flow situations contain-ing strong shock waves; in the lattercase, the necessary scatteringparticles or aerosols in the flow do

not follow the sudden changes inflow speeds or directions. Themethod has further advantages:the measurement procedures arecompatible with the productiontesting environment of large-scalewind tunnels, the experimental setupis relatively simple, and the systemcould be operated by trained wind-tunnel technicians as a productioninstrument.

Point of Contact: R. McKenzie(650) [email protected]

Pressure-Sensitive Paintand Photogrammetry forAeroelastic ExperimentsEdward T. Schairer,Lawrence A. Hand

Methods for predicting theaeroelastic stability of aerospacestructures are generally based onlinearized aerodynamic theory. Theaccuracy of these methods sufferswhen nonlinear flow features (forexample, shock waves, vortices,separated flow) interact with theaircraft structure. For example, attransonic speeds, where significantshock waves may be present, two-and three-dimensional wings tend toflutter at lower dynamic pressuresthan predicted by linear flutteranalyses.

Since the late 1970s, consider-able progress has been made inusing computational fluid dynamics(CFD) to account for nonlinearaerodynamics in aeroelastic analy-

ses. Before these more powerfulmethods can be of practical value toaircraft designers, however, theymust be tested by comparing theirresults with reliable experimentaldata. In particular, it is important toverify that unsteady, nonlinearaerodynamic features and theirinteractions with the structure areproperly represented.

To help address this need,simple, small-scale, aeroelasticexperiments were conducted in theHigh Reynolds Number Channel 2(HRC-2) at Ames Research Center.The objective of the experimentswas to (1) evaluate the use ofpressure-sensitive paint (PSP) tomeasure unsteady pressure distribu-tions on aeroelastic models and(2) stereophotogrammetry to mea-sure unsteady model deformations.Semispan, clipped delta-wingmodels built from thin flat plateswere tested at transonic speeds.The models were imaged by threesynchronized black-and-white videocameras, and the data were recordedon videotape. Correlated imagesfrom two of these cameras wereused to estimate the space coordi-nates of reference marks on themodel at each instant, and themotion of each mark was estimatedby fitting the deflection data with adamped sinusoid. The third camerawas used for PSP.

All the procedures needed tomeasure unsteady pressure distribu-tions using PSP were successfullydemonstrated. The PSP measure-ments were seriously compromised,however, because the response timeof the pressure paint was too slow,resulting in significant attenuation


of the unsteady component of thePSP signal. The first figure presentstypical PSP data from a run(Mach = 0.85), where the wingtipwas deflected and released. The graylevels in the image (part (a)) whichwas acquired just after the wingtipwas released, are proportional to thepressure coefficient. Part (b) of thefigure compares the pressure coeffi-cient along a spanwise line from rootto tip with steady data acquired afterthe unsteady transient had disap-peared. Note that the suction peakassociated with the leading-edgevortex has moved outboard in thesteady condition.

The second figure presentsphotogrammetry data acquiredduring a run at Mach = 0.85, wherethe tip of the model was unre-strained as the pressure in the tunnelwas slowly increased. Part (a) of thefigure shows the time history of thedeflection of the wingtip at threedynamic pressures just before themodel became unstable; part (b)shows the phases and amplitudes ofpoints on the wing compared withthe trailing edge of the wingtip. Theonset of instability was marked by alarge increase in the amplitude ofthe motion, as well as an increase inthe phase difference between theleading and trailing edges.

This work is a first step in usingPSP and photogrammetry to docu-ment complex, unsteady aeroelasticresponses. Once these techniquesare further refined, they can be usedto better understand these responsesand to help validate higher-orderaeroelasticity methods. A natural

Fig. 1. PSP image of flexible wing and corresponding pressure coefficientalong x/C = 0.75.

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extension of this work is to applyPSP and photogrammetry to tests ofhelicopter rotor blades.

Point of Contact: E. Schairer/L. Hand(650) 604-6925/[email protected]@mail.arc.nasa.gov

Visualizing Wind-TunnelExperimental DataSamuel P. Uselton, Glenn Deardorff,Leslie Keely, Yinsyi Hung, Arsi Vaziri

A new software tool that dis-plays data collected during wind-tunnel tests and that supportsinteractive analysis of those data hasbeen developed at Ames ResearchCenter. The tool, called exVis,allows visualization and interactionmethods frequently used in analyz-

ing computational results to beapplied to experimentally collecteddata. This product is a step towarddeveloping a unified environmentfor analyzing data from multiplesources. The ability of researchersand engineers to display and interactwith data from a variety of sourceswithin a single visualization environ-ment will increase the understandinggained from the data and reduce thetime required.

The initial product, exVis 1.0,was developed for data collected

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Fig. 2. Deflection of wingtip trailing edge, and phase difference and amplitude ratio with respect to tip trailing edge.


using a pressure-sensitive paint (PSP)system. The exVis software packagereads a Flexible Image TransportSystem (FITS) format file producedby the PSP data-acquisition systemwhich contains pressure values, anddisplays these data as an image in awindow (“ImageViewer” shown atleft in the figure (see Color Plate 9 inthe Appendix)). The image can bedisplayed using a gray scale or apseudocolor mapping of data toscreen intensity.

Users can select tools that allowthe selection of a “slice” of data fromthe image along a line segment. Thisslice is then graphed in a separatewindow (“GraphViewer,” at the rightin the figure) that shows how thecoefficient of pressure varies alongthe length of the slice. Several slicescan be selected from the same imageand graphed on the same axes, ordifferent slices (or sets of slices) canbe graphed in separate windows.Multiple ImageViewers can eachdisplay an image, with selectedslices graphed together or separately.The ImageViewer and GraphViewercan each be queried interactivelyto show the data value at thecursor; the GraphViewer alsodisplays the corresponding locationin the ImageViewer. The user canchange the sizes and positions ofImageViewers and GraphViewers.

Previously selected slices or graphscan be deleted, and a graph can beprinted via postscript. A user cansave the current status and restorethe program to that state at a latertime. An on-line help feature is alsoincluded.

Although exVis was developedspecifically with PSP data acquisi-tion in mind, it is sufficiently robustto work with other scalar data thatare provided in FITS format, andcould be easily adapted for dataprovided in other two-dimensionalarray formats. ExVis 1.0 was com-pleted in July 1996 and integratedwith other Ames-developedsoftware for use in a wind-tunneltest (September 1996).

Point of Contact: S. Uselton(650) [email protected]

Surface Tension Effectson Skin FrictionMeasurementsG. Zilliac, A. Celic

The Fringe-Imaging skin frictiontechnique (FISF), which was origi-nally developed by Monson andMateer at Ames Research Centerand recently extended to three-dimensional flows, is the mostaccurate skin-friction measurementtechnique currently available. Theprinciple of the FISF is that theskin friction at a point on an aero-dynamic surface can be determinedby measuring the time-rate-of-change of the thickness of an oildrop placed on the surface under theinfluence of the external air bound-ary layer. Lubrication theory is usedto relate the variation in oil-patchthickness to shear stress.

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The uncertainty of FISF measure-ments is estimated to be as low as4%, yet little is known about theeffects of surface tension and wall-adhesion forces on the measuredresults.

A modified version of the free-surface Navier-Stokes solver RIPPLE,developed at Los Alamos NationalLaboratories, was used to computethe time development of an oil dropon a surface under a simulated airboundary layer. RIPPLE uses theVolume of Fluid (VOF) method totrack the surface and the ContinuumSurface Force (CSF) approach tomodel surface tension and wall-adhesion effects.

The figures show the develop-ment of an oil drop over a period ofabout 4 seconds. The profile of thedrop (first figure) rapidly changes

from its initial circular-arc shape to awedge-like shape. The close agree-ment between the oil-drop thicknesscomputed using RIPPLE and theresults obtained with a greatlysimplified numerical model of oil-drop flow (solution of Squires oil-drop equation which does notinclude surface tension and wall-adhesion effects) proves that surfacetension will have a negligible effecton FISF results (second figure).

Point of Contact: G. Zilliac(650) [email protected]

.01 .1 1 10.001

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Fullerene Gear Design,Simulation, andVisualizationAlbert Globus

Ames Research Center hasdesigned and computationallyinvestigated a series of atomicallyprecise gears based on fullerenechemistry (see first figure). Thesegears are approximately 1 nanom-eter in diameter and can turn at upto 100 gigahertz according tocomputer simulations. Long-rangegoals include the design and valida-tion of programmable molecularmachines that can replicate andbuild useful aerospace products.This work will require massivecomputer power as nanotechnologyresearch moves from “what if” to“how.” The current simulations helpin understanding these computa-tional requirements. If successful,molecular nanotechnology couldrevolutionize aeronautics and spacetechnology by producing materialswith radically improved strength-to-weight ratios and active materialsfilled with atomically precisemachines that react to the environ-ment and that can self-repair.

Hypothetical nanotechnologymaterials based on diamond chemis-try have great potential, but atpresent no clear path can be seen fortheir synthesis. In contrast, fullerenes(closed-cage carbon molecules) arenow routinely produced in the


laboratory. The carbon form calledC-60 (a molecule with 60 carbonsarranged in a soccer-ball-likeconfiguration) is produced commer-cially, and carbon nanotubes havebeen produced in bulk, some over100 microns long. It is possible toadd a wide variety of molecularfragments to C-60 and otherfullerenes. In particular, benzynewill react with the C-60 under mildlaboratory conditions to formappended structures similar togear teeth.

A series of videos has beenmade including gear synthesis steps,favorable operating conditions,various gear configurations, a rack-and-pinion system (see secondfigure), and tooth slip conditions,which are all based on moleculardynamics simulations run on parallelcomputers. Each gear consists of acarbon nanotube with severalO-benzyne fragments added to formgear teeth. Molecular dynamicssimulations suggest that when onegear is rotated, intermolecular forcescause the second gear to rotate at upto 100 gigahertz without slippage orfragmentation.

Point of Contact: A. Globus(650) [email protected]

Fig. 1. Hypothetical carbon nanotube gears. Each gear is approximately1␣ nanometer in diameter. Simulations suggest this system can rotate at upto 100 gigahertz.

Fig. 2. Hypothetical rack-and-pinion system built from functionalizedfullerene nanotubes.

51



GLOBAL CIVIL AVIATION/ENVIRONMENTAL COMPATIBILITY

Civil Tiltrotor NoiseAbatement ApproachesWilliam A. Decker,Rickey C. Simmons

A civil tiltrotor regional transportoperating from vertiports near urbanand business centers offers consider-able potential for relieving conven-tional airport runway congestion.Flight operations near urban areasmust also minimize noise effectswhile providing for all-weatherschedule reliability. Conversion fromairplane-mode flight to a helicopter-like landing while minimizing noisepresents both a challenge and anopportunity for tiltrotor aircraft. Theintroduction of worldwide aircraftposition information with the GlobalPositioning Satellite system providesan economic guidance source tosupport the desired low-noise,all-weather operations.

Initial tiltrotor noise-abatementlanding approach profiles wereconstructed based on actual noisemeasurements of the XV-15 tiltrotorresearch aircraft. Instead of aconventional landing approachwhich intercepts and tracks down a3-degree glideslope, two alternativeprofiles were constructed, bothfeaturing an initial 3-degree descentwhich changes to a steep 9-degreedescent close to the landing spot(first figure). Based on the XV-15noise data, the steeper finalapproach path offers good potentialfor reducing noise while providingbetter clearance of obstacles near

the vertiport. Depending on theterrain and airspace constraintsassociated with nearby conventionalairports, the initial approach seg-ment involved conducting either alevel-flight conversion toward thehelicopter-mode landing configura-tion, or performing all of the conver-sion in descending flight. Bothapproach profiles carefully specifiedairspeed, descent rate (flightpathposition) and proprotor tilt anglebased on the distance from thelanding spot.

Cockpit displays and controlfeatures have been developed tohelp guide pilots to reliably andeasily fly these complex approachprofiles in all-weather conditions. Asillustrated in the second figure, thedisplays were adapted from modern

electronic display formats fortransport aircraft. Pursuit guidanceusing flightpath vector symbols,adapted from military head-updisplay designs, has been developedfor tiltrotor use and applied to thepanel-mounted electronic displays.

The unique large-motion cueingcapability of the Vertical MotionSimulator (VMS) at Ames ResearchCenter contributed to pilotedevaluations of approach profilesand displays. Use of a visual scenebased on the San Francisco BayArea, developed in the VMSSIMLAB, contributed to the evalua-tion scenario and provided geo-graphic rationale for the complexapproach flightpath. Eleven pilotsrepresenting NASA, the FAA, BritishCAA, and the rotorcraft industry

G L O B A L C I V I L A V I A T I O N / E n v i r o n m e n t a l C o m p a t i b i l i t y

GLOBAL CIVIL AVIATION/ENVIRONMENTAL COMPATIBILITY Nacelle deceleration

for landing fromLanding Decision Pointat 200 ft altitude

180/0 <- 250/0

180/0

250/0

3000 ft altitude

2000 ft altitude

140/30

140/30

110/60

3°

3° initialglideslope

9° finalglideslope

9°

110/60

Fig. 1. Tiltrotor noise-abatement approach profiles with two-segmentflightpaths. Altitude (flightpath angle), airspeed, and nacelle angle (forexample, 110/60°) are specified as functions of distance from landing.

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evaluated the approaches anddisplays, and provided commentsfor further refinement.

Point of Contact: W. Decker(650) [email protected]

XV-15 Blade-VortexInteraction NoiseC. W. Acree, Megan S. McCluer,Cahit Kitaplioglu

As part of the continuingIn-Flight Rotorcraft AcousticsProgram, flight tests of the XV-15tiltrotor were completed and wind-tunnel tests are under way. Programobjectives are (1) to use the NASAAmes YO-3A acoustic researchaircraft to measure blade-vortexinteraction (BVI) noise from rotor-craft in flight and to make compari-

sons with similar wind-tunnelmeasurements, (2) to use thesecomparisons to better understandBVI noise, and (3) to determine howto minimize BVI noise on rotorcraft.

During the flight portion of thistest, the YO-3A fixed-wing aircraftused a wing-tip-mounted micro-

phone to measure BVI noise gener-ated by the XV-15 tiltrotor. Fourflights were performed with theYO-3A and XV-15 flying in closeformation, as shown in the figure.The flight conditions and micro-phone location were chosen tomeasure the most prominent BVInoise. The starboard wing-tipmicrophone of the YO-3A waspositioned 20 degrees below theright rotor hub of the XV-15 andoffset to the right to pick up BVIsoccurring at a rotor azimuth of150 degrees (see figure). The dis-tance between the starboard wing-tip microphone and the rotor hubwas 3 rotor diameters (75 feet).Target flight conditions includedadvance ratios of 0.165 and 0.185,tip Mach number of 0.69, a rotorweight coefficient of 0.0111, anddescent rates of 300–1100 feet perminute.

The results of the flight test wereused to determine equivalent testconditions for a series of tests of theXV-15 rotor in the National Full-Scale Aerodynamics Complex

Fig. 2. Pilot’s view on approach to urban vertiport. Electronic cockpitdisplays provide guidance for complex noise-abatement approach profiles.

Fig. 1. YO-3A and XV-15 in formation flight.


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(NFAC) 80- by 120-Foot WindTunnel test section at Ames ResearchCenter. A single (right-side) rotor wasmounted on the Rotor Test Appara-tus (RTA), and microphones wereplaced in locations geometricallyidentical to the relative positions ofthe YO-3A microphones and XV-15rotor during flight. The data from theNFAC tests have been comparedwith the flight data to validate thewind-tunnel test and the measure-ment methods. Although very goodqualitative agreement was achieved,good quantitative agreement has yetto be demonstrated. In particular, theability to match wind tunnel withflight will likely require very goodcharacterization of the flight operat-ing conditions to enable matching ofthe exact test condition in the windtunnel.

Point of Contact: C. Acree(650) [email protected]

Tiltrotor AeroacousticModelLarry Young

NASA conducts tiltrotorresearch programs in order to meetnational requirements for militaryand civilian tiltrotor aircraft. Thisresearch requires moderate-to-large-scale wind-tunnel testing of tiltrotormodels. Such testing provides thedata necessary to confirm aero-acoustic prediction methods, andto investigate and demonstrateadvanced civil tiltrotor and high-speed rotorcraft technologies.

In 1991, NASA established thatit had a requirement to gain an

improved understanding of theaeroacoustic characteristics oftiltrotor aircraft and, therefore,initiated the development of twohardware-compatible test rigs: anisolated-rotor test stand and a full-span model (dual rotors with acomplete airframe representation).These two test stands are inclusivelycalled the Tilt Rotor AeroacousticModel (TRAM). The isolated rotortest stand is not a stand-alone unit,but is instead intended to be com-posed chiefly of major subassem-blies of the full-span configuration.

The TRAM will be used as a testbed for testing moderate-scale tilt-rotor models in two different testconfigurations in different researchfacilities: (1) isolated rotor testing atthe Duits-Netherlands Windkannal(DNW) in The Netherlands; and(2) isolated rotor and full-spantesting at the National Full-ScaleAerodynamics Complex (NFAC) atAmes Research Center.

A checkout test of the TRAMisolated-rotor test stand was con-

ducted in the NFAC N246 ModelPreparation building at Ames.The checkout testing included theacquisition of hover data—includingrotor airloads data—for a 1/4-scaleset of proprotor blades using theNFAC NPRIME data-acquisitionsystem. Key test-stand capabilitiesbeing checked out include a rotatingamplifier system (RAS) developedby the Nationaal Lucht-enRuimtevaartlaboratorium (NLR)and the Monitoring Front-End DataSystem (MFEDS) real-time safety-of-flight monitoring system. Aconsiderable amount of infrastruc-ture buildup—including armor-plateshielding and control room installa-tion—was required in the N246building to enable TRAM functionaltesting.

The full-span version of theTRAM test stand is also beingconcurrently developed. Fabricationof full-span model development isunder way (see figure). A newgeneration rotor-control console for

Fig. 1. Full-span TRAM fabrication and assembly.


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the isolated rotor test and the full-span model is also in development.

The 1/4-scale TRAM rotors andairframe are based on the design ofthe V-22 Osprey tiltrotor aircraft.The TRAM test stand will also be anadvanced technology demonstratorplatform for the Short Haul CivilTiltrotor (SH(CT)) program, a sub-element of the Advanced SubsonicTechnology (AST) initiative. BothBoeing and Sikorsky Aircraft havebeen contracted by the NASASH(CT) program to develop interfacehardware to test a new generation ofsmall-scale, advanced proprotors onthe TRAM test stand.

Point of Contact: L. Young(650) [email protected]

Predicting and AnalyzingRotorcraft NoiseRoger C. Strawn, Rupak Biswas,Lenny Oliker

Aerodynamic noise is a majorproblem for future civil tiltrotordesigns. Noise is a particular prob-lem during landing when the rotor-wake system is pushed up into therotating blades. The resulting blade-vortex interaction (BVI) noise canbe unacceptable in urban environ-ments. All four of the major U.S.helicopter companies have activeresearch programs with the objectiveof reducing tiltrotor and helicopterBVI noise.

Three things are required inorder for rotor designers to system-atically reduce BVI noise: (1) animprovement in the accuracy of far-field noise predictions; (2) the ability

to analyze those predictions in away that identifies the sources of theoffending noise; and (3) control ofrotor-blade motion in ways thatreduce the noise. Researchers atAmes Research Center have recentlydeveloped new acoustic predictionand analysis tools that directlyaddress the first two of these threeobjectives.

The new acoustic predictionscheme combines computationalfluid dynamics (CFD) with Kirchhoffintegration methods. The CFDmethods compute the nonlinearaerodynamics and acoustics close tothe rotor blades, and the Kirchhoffintegrations carry the acousticinformation to the far-field in acomputationally efficient manner.These CFD/Kirchhoff methods runon the IBM SP-2 parallel computerto facilitate the computation of time-accurate acoustic information overlarge regions of space. Computeraudio and visual rendering (seefigure) of the resulting far-field

acoustic propagation allows rotordesigners to “see and hear” the noisein the far-field. Computer animationsof the far-field noise propagationconvey much more information thancan be obtained from typical rotor-noise experiments, in which thedata are limited to those pickedup by a few far-field microphones.In addition to the new predictionand visualization tools, the CFD/Kirchhoff analysis can be modifiedto highlight the sources of noise onthe Kirchhoff surface. This allows arotor designer to pinpoint the originsof the far-field noise and to modifythe blade trajectories to minimizethe blade-vortex interactions.

The new prediction and analysistools will have applications to avariety of helicopter and tiltrotorgeometries.

Point of Contact: R. Strawn(650) [email protected]

Fig. 1. Computed acoustic pressure contours for the AH-1 Cobra helicopter.


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Airframe NoiseMeasurements:Atmospheric PressureW. Clifton Horne, Julie A. Hayes,Michael E. Watts, Paul H. Bent

With the trend toward quieter,higher bypass-ratio engines incommercial transport aircraft,airframe noise is a significantproblem during approach andlanding. In support of the NoiseReduction Element of the AdvancedSubsonic Technology (AST)Program, an aeroacoustic test of anunpowered, 4.7%-scale McDonnellDouglas DC-10 was conducted inthe NASA Ames 40- by 80- FootWind Tunnel (see figure). Acousticalmeasurements included streamwisetraverses of four microphones, far-field measurements with directionalmicrophones using parabolicreflectors, and noise-source locationwith a 40-element phased micro-phone array. Aerodynamic measure-ments included steady and unsteadywing-surface pressures and modelincidence.

The primary objectives of thistest were to (1) assess the feasibilityof extrapolating wind-tunnel air-frame noise measurements forcomparison with full-scale flight-testresults, (2) locate prominent noisesources with the acoustic array,and (3) evaluate prototype noise-reduction concepts on a realistictransport configuration.

Measurements supporting allof the primary test objectives wereobtained. In particular, acousticimages of airframe noise sources onthe high-lift system and landing gearwere obtained. This was achievedusing the Microphone Array Phased

Processing System developed atAmes Research Center.This system used high-performancegraphical workstations in the controlroom to process the array data anddisplay results during the test. Thesystem processed 200 frequencies ateach data point within 30 minutes,thus allowing all test data to beprocessed during the test (as much

as 3 months of posttest processingwere required in previous tests). Theprocessing system was designed tofully support existing remote accesswind-tunnel capabilities.

Studies of flap-edge fencesdesigned to reduce noise emanatingfrom the flap edge showed broad-band noise reduction levels of

Fig. 1. DC-10 model in the Ames 40- by 80-Foot Wind Tunnel.


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3–4 decibels. Correlation of thenoise signals on a far-field micro-phone with the unsteady pressuresignals on the model aircraft surfacewas effective in locating the sourceof the airframe noise.

Point of Contact: C. Horne(650) [email protected]

Airframe NoiseMeasurements: Pressuresto 4.7 AtmospheresW. Clifton Horne, Stephen M. Jaeger,Mahendra Joshi, James R. Underbrink

Airframe noise, primarilyattributable to the landing gear,leading-edge slat, and trailing-edgeflap, is known to be a significantcomponent of the approach andlanding noise of commercial trans-port aircraft. The NASA AdvancedSubsonic Technology (AST) NoiseReduction Technology Program issponsoring several measurement andprediction programs in order toreduce airframe noise by 4 decibelsbelow 1992 levels. Because of theexpense of flight tests, an importantelement of this research is theapplication of new measurementtechnology, such as the multisensorphased acoustic array, on tests ofsmall-scale wind-tunnel models andthen scaling and extrapolating thesemeasurements to full-scale. Thephysics of aerodynamic noisegeneration and the effect of geomet-ric scale are highly complex and not

well understood. Therefore, acousticmeasurements, over a range of scalefactors (or Reynolds numbers), arerequired to identify the importantnoise sources on full-scale aircraftand to determine the scaling lawsthat will permit accurate full-scalepredictions from small-scale tests.

Recent successful tests by Amesand Boeing using a multielementphased microphone array in closed,untreated test sections suggested thatuseful airframe noise measurementscould be obtained in the Ames12-Foot Pressure Wind Tunnel(PWT) for variable Reynolds numbertesting. Feasibility tests of a Boeing52-element array in the 12-FootPWT were planned in two phases.An initial study of the operationalfeasibility was planned with the testsection empty except for a surveystrut, model ground plane, andcalibration noise sources. If thisinitial study proved to be successful,a second demonstration of aero-acoustic measurements of a4.7%-scale DC-10 was planned inconjunction with McDonnellDouglas to acquire the first variableReynolds number airframe noisemeasurements. The results would becompared with atmospheric mea-surements acquired from the samemodel in the 40- by 80-Foot WindTunnel at Ames with a 40-elementphased-array designed andassembled at Ames.

The first feasibility test demon-strated that the microphone-arraysystem (sensors, cabling, signalacquisition and processing, andcomputer networking) could be

accommodated with existing facilitysupport infrastructure. Severalaeroacoustic noise sources werelocated with the array, associatedwith support struts and the trailingedge of the semi-span groundplane. The second test utilizing the4.7%-scale DC-10 aircraft modelwas then undertaken. During thissecond test, the Boeing arrayacquired noise measurements to60␣ kilohertz, corresponding to about3 kilohertz full-scale, and identifiednoise sources at atmosphericpressure which correspondedclosely with sources identified inthe previous 40- by 80-Foot WindTunnel test (see figure (see ColorPlate 10 in the Appendix)). Inaddition, noise measurementswere obtained for pressures up to4.7 atmospheres. Preliminaryevaluation of these measurementsshow that the relative strength of thenoise sources varies with Reynoldsnumber in a complex and as yetunpredictable manner, stressingthe need for large-scale, high-Reynolds-number validation ofnoise-prediction methods.

Point of Contact: C. Horne(650) [email protected]


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R E V O L U T I O N A R Y T E C H N O L O G Y L E A P S / I n n o v a t i v e T e c h n o l o g y a n d T o o l s

REVOLUTIONARY TECHNOLOGY LEAPS/INNOVATIVE TECHNOLOGY AND TOOLS

X-36 Pioneers AdvancedAerodynamics and FlightControlsRodney Bailey, Mark Sumich

The X-36 project is pioneeringthe development of advancedaerodynamics and flight controltechnologies that will permit theconcurrence of low radar observa-bility, agility, and supersonic speedin a single design. Prior to the X-36technologies, these features weremutually exclusive. The flightevaluations of the X-36 aircraft, ajoint NASA/McDonnell Douglasproject, are currently under way atthe Dryden Flight Research Center.

The project began in February1994 after several years of researchand concept development in theAmes facilities by both Ames andMcDonnell Douglas engineers.

The project involves the design,fabrication, and flight evaluation oftwo unmanned aircraft. The 10-foot-span flight articles are about 18 feetlong and 3 feet high and weigh1250 pounds.

Features of the X-36 includemultifunction wing trailing edgecontrol surfaces, combined ailerons,split ailerons and flaps, wing leadingedge flaps, and all moving canards.The aircraft has neither vertical norhorizontal aft tail surfaces. Theaircraft (shown in the figure) isnaturally unstable in both the pitchand yaw directions, with artificialstability provided by the control lawsutilizing both aerodynamic andpropulsion forces.

The flight testing at Dryden willevaluate real-time stability marginand will determine aerodynamic,stability, and control data on theconfiguration using the parameter-identification derivative.

Point of Contact: R. Bailey(650) [email protected]

Closed-Loop NeuralControl of RotorcraftVibrationSesi Kottapalli

A study on identification andcontrol of rotorcraft hub loads(vibration) using neural networkshas been initiated at Ames ResearchCenter. Neural control simulationcovers both identification andcontrol of hub loads, where a metricis used to represent the hub loadcomponents. The closed-loopcontroller must be computationallyefficient, it must converge quickly(in six iterations or less), andgradient-based methods mustnot be used.

The program objective is toimplement closed-loop neuralcontrol of rotorcraft vibration ina wind tunnel in two phases:(1) conducting neural-controlsimulations using existing individualblade-control wind-tunnel test data,and (2) implementing closed-loopneural control during a future full-scale rotorcraft wind-tunnel test(contingent on first-phase resultsbeing sufficiently promising).

The identification (plant model-ing) procedure, which involves theuse of a two-hidden-layer radialbasis function neural network, hasbeen completed. The procedure hasbeen extended to multi-input, multi-output applications. A simple,straightforward-to-implement neural-control technique, the “directinverse” method, was selected,successfully applied, and found to

REVOLUTIONARY TECHNOLOGY LEAPS/␣ ␣ INNOVATIVE TECHNOLOGY AND TOOLS

Fig. 1. X-36 Tailless Fighter Agility Research Aircraft prepares for flight at theDryden Flight Research Center.

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be robust. The present approach (seethe figure) has the following essentialingredients: accurate plant model-ing, halving of the metric in order toaccelerate controller convergence,“inverted-axes” control modeling,and a feedback iterative loop. Aback-propagation neural networkused in the control step has beensuccessful. Current results show thata 66% reduction in baseline rotorvibratory hub loads is achievable inonly four controller iterations. Alimited-scope comparison of theresults from the present neural-control procedure with those froma one-step deterministic controllershowed that the two control meth-ods are comparable, with neuralcontrol being more robust.

Point of Contact: S. Kottapalli(650) [email protected]

Coupled Navier–Stokesand Optimizer Analysisof a Transonic WingRoxana M. Greenman,Samson Cheung, Eugene L. Tu

Numerical optimization can beused as a means of studying theeffects of the geometric parameterson the aerodynamics of a wing.Different types of aerodynamicnumerical-optimization techniquesthat have been researched in recentyears have been found to needimprovement. New optimizationtools must be developed to provideefficient means for improving thedesign process and understandingthe flow physics. The overall objec-tive is to develop the necessary toolsneeded to help, using computationalfluid dynamics for the design ofadvanced wings through the inclu-sion of new, promising optimization

modules to the code OVERFLOW.The object is to demonstrate the useof a numerical-optimization routineto understand the significance ofdifferent geometric parameters onthe aerodynamics of a wing.

This study demonstrated howone optimizer package is used tostudy the flow physics of a transonicwing. This numerical-optimizationroutine is integrated with a gridgenerator and a validated Navier–Stokes flow solver. The effects ofwing sweep angle, root and tip twistangles, dihedral, and angle of attackon the lift-to-drag ratio are studiedusing surface-pressure contours andpressure distributions. The resultsshow that when lift-to-drag ratiois increased using single designvariable optimization, the resultinglift coefficient falls below theoriginal value. The angle of attackmust be increased in order topreserve the original lift coefficientwith the modified geometry. A betterway to find the optimal configura-tion with the highest lift-to-drag ratiois by first optimizing with multipledesign variables (see the figure (seeColor Plate 11 in the Appendix)),then including the angle of attack inthe design loop with lift constrainedto the original value. This methodshowed an improvement of 2.4%(with constant lift) in the lift-to-dragratio.

Point of Contact: R. Greenman(650) [email protected]

Plantmodel

Half-intervalmethod

(user specifiedmetric reduction)

Invertedneural network

for control(supplies newcontrol input)

Controlphase input

Actualmetric

Present Closed Loop Neural Control Simulation(“metric” refers to vibratory hub loads metric)

Desiredmetric

Updatedcontrol phaseinput

Fig. 1. Inverted neural network for vibration control.


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Parallel UnstructuredMesh AdaptionRupak Biswas, Leonid Oliker,Roger Strawn

Computational methods to solvelarge-scale realistic problems canbe made more efficient and costeffective by using them in conjunc-tion with dynamic mesh adaptionprocedures that perform coarseningand refinement to capture interestingsolution features. Such adaptiveprocedures evolve with the solution,and they provide scientists a robustand reliable methodology to obtainsolutions on adapted meshes that arecomparable to those obtained onglobally fine grids but at a muchlower computational cost. In addi-tion, with the popularity of distrib-uted computing, parallelunstructured mesh adaption proce-dures are absolutely imperative.

An efficient solution-adaptiveprocedure has been developed forthe simultaneous coarsening andrefinement of unstructured tetrahe-dral meshes. An innovative datastructure, which uses a combinationof dynamically allocated arrays andlinked lists, allows the mesh connec-tivity to be rapidly reconstructedafter individual points are addedand/or deleted. The data structure,based on edges of the mesh ratherthan the tetrahedral elements, notonly enhances the efficiency butalso facilitates anisotropic meshadaption. This scenario means thateach tetrahedral element is definedby its six edges rather than by its fourvertices. Each edge, in turn, main-tains a list of all the elements thatshare it. Thus, elements that need to

be modified can be rapidly identifiedwhen an edge is inserted or deleted.Regions of the mesh that need to beadapted are identified by markingthe edges based on an error indica-tor. The adaption procedure for eachelement is determined from a binarypattern that depends on which of itssix edges are marked. The edge datastructures and pattern markingensure that the refinement andcoarsening procedures can beperformed efficiently.

The parallel mesh adaptionprocedure has been used to modelthe high-speed impulsive noise for aUH-1H helicopter rotor in hover. Acoarse mesh is initially generatedand additional points are dynami-cally added to capture the acousticwave and the shock near the tip.Mesh coarsening is used to removeunnecessary points from regionswith smooth solutions; thus, existinggrid points are redistributed in amore efficient manner. A close-up ofthe final grid and pressure contoursin the plane of the rotor after threeadaption steps is shown in the figure(see Color Plate 12 in the Appendix).Results show excellent agreementwith experimental microphone datafor far-field acoustic pressure.Parallel speedup depends on thefraction of the mesh that is adapted.When 33% of the mesh was refined,a speedup of 43.2X was obtained on64 processors. The speedup im-proved to 51.5X when 60% of themesh was refined.

Current results demonstratesignificant gains in computationalefficiency when the parallelsolution-adaptive method is com-pared to its fixed-grid counterparts.

These improvements are necessaryfor future high-fidelity simulations ofrealistic problems in unsteadyenvironments.

Point of Contact: R. Biswas(650) [email protected]

Load Balancing AdaptiveUnstructured MeshesRupak Biswas, Leonid Oliker,Andrew Sohn

Mesh adaption is a powerfultool for efficient, unstructured-gridcomputations, but it causes loadimbalance among processors on aparallel machine. A novel methodhas been developed to dynamicallybalance the processor workloadswith a global view. A dual graphrepresentation of the initial computa-tional mesh keeps the complexityand connectivity constant during thecourse of an adaptive computation.It is a portable system for efficientlyperforming large-scale adaptivecalculations in a parallel message-passing environment.

The first figure depicts theframework used for parallel adaptivescientific computations. Meshadaption, repartitioning, processorassignment, and data remapping arecritical components of the frame-work that must be accomplishedrapidly and efficiently so as not tocause a significant overhead to thenumerical simulation. The unstruc-tured mesh is first partitioned andmapped among the availableprocessors. A solver then runs forseveral iterations, updating solution


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variables. After an acceptablesolution is obtained, the meshadaption procedure is invoked. Itfirst targets edges of the mesh forcoarsening and refinement based onan error indicator computed fromthe numerical solution. The oldmesh is then coarsened, resulting ina smaller grid. Since edges havealready been marked for refinement,it is possible to exactly predict thenew mesh before actually perform-ing the refinement step. Programcontrol is thus passed to the loadbalancer. If a quick evaluation stepdetermines that the new adaptedmesh will be unacceptably loadbalanced, a repartitioner divides themesh into subgrids. The new parti-tions are then assigned to theprocessors in a way that minimizesthe cost of data movement. If theremapping cost is less than thecomputational gain that would beachieved with balanced partitions,all necessary data are appropriatelyredistributed; otherwise, the newpartitioning is discarded. Thecomputational mesh is then actuallyrefined and the numerical calcula-tion is restarted.

An extensive study with acomputational mesh used to simu-late a UH-1H helicopter rotor bladeacoustics experiment indicated thatthe load-balancing scheme iseffective for large-scale scientificcomputations on distributed-memorymachines and scales excellently withthe number of processors. Thesecond figure shows how the totalexecution time was spent in eachmodule of the framework when themesh was refined to be more thanfive times larger than the original.

Initialization

NY

YN

Mesh adaptor Load balancer

Initial mesh

Partitioning

Mapping

Remapping

Expensive?

Reassignment

Repartitioning

Balanced?Edge marking

Coarsening

SolverRefinement

24 32 40 48 56 641680

10–2

10–1

100

101

102

10–3

10–4

10–5

Number of processors

Exe

cuti

on

tim

e (s

ec)

Adaption

Remapping

Reassignment

Partitioning

Fig. 1. Framework for parallel adaptive scientific computation with loadbalancing.

Fig. 2. Anatomy of total execution time.


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The processor reassignment timesare almost negligible compared tothe other times. The repartitioningtime is generally independent of thenumber of processors. Both theadaption and remapping timesgradually decrease as the numberof processors is increased. Thesesample results show that none ofthe individual modules will be abottleneck on massively parallelmachines.

Point of Contact: R. Biswas(650) [email protected]

Initial Release of the FieldEncapsulation LibrarySteve Bryson

Computational fluid dynamics(CFD) simulations are a new way ofdesigning and evaluating aircraftdesigns on a computer. CFD simula-tions are computed at many points,forming a three-dimensional grid inspace. The variety of grid types cangreatly complicate the task of usingcomputer graphics visualization toinvestigate the CFD simulations (seethe figure (see Color Plate 13 in theAppendix)). Visualization algorithmscan depend very strongly on the typeof grid; an algorithm written for onegrid type may not work on anothergrid type. This problem is particu-larly acute when developing ageneral-purpose visualization systemfor CFD. The objective of the FieldEncapsulation Library (FEL) projectis to solve the grid-dependence

problem by implementing a librarythat provides a grid-independentapproach to CFD data access. UsingFEL, a single visualization algorithmcan work on a variety of grid types.Very high performance data accessis an additional objective in order tosupport interactive visualization,which allows intuitive explorationof the simulated flow phenomena.Another objective of FEL is toprovide programmers with the abilityto access, organize, and manipulatefield-type data on many types ofnumerical grids at the same time.

FEL was fully implemented andreleased for structured multizoneand unstructured grid types, provingthe grid-independence concept.Data access times averaging0.0002 second per access weremeasured. These capabilitiesallow the development of high-performance visualization algorithmsthat will work for all supported gridtypes. FEL has been integrated intothe Virtual Windtunnel as well asother individual visualizationsystems. The concepts behindFEL were presented at Visualization‘96, an IEEE peer-reviewed confer-ence held in October 1996 inSan Francisco, California.

FEL is an example of a “horizon-tal product,” a set of softwarelibraries that can be used in a varietyof applications, significantly reduc-ing the time required to implement anew visualization system.

Point of Contact: S. Bryson(650) [email protected]

RANS-MP: PortableParallel Navier–StokesSolverR. Van der Wijngaart,Maurice Yarrow

Efficient, cost-effective solutionof flow problems of interest to theaircraft industry requires competi-tively priced hardware and maintain-able, portable software. The currentgeneration of parallel computersprovides that hardware, and stan-dard system software such as themessage passing interface (MPI)library provides half of the softwaresolution. The other half comes fromapplication programs that employalgorithms that are tolerant ofdifferences in specific machineparameters, most notably the speedwith which the processors in aparallel computer can exchangedata. The Reynolds-averagedNavier–Stokes with multipartitioning(RANS-MP) program has beenspecifically designed to meet theserequirements.

The newly developed RANS-MPflow solver program employs theadvanced, bidirectional, multi-partition algorithm. This methodlimits data movements betweenprocessors to a minimum, renderingit insensitive to the peculiaritiesof different parallel computers.RANS-MP uses the widely availableMPI, which means it can runefficiently on most of today’s parallelmachines. It also employs a pilot


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version of MPI’s companion input/output (I/O) library MPI-I/O, whichallows efficient scheduling ofpreviously prohibitively expensiveparallel read and write operations.

The first figure shows theperformance of the program on theAmes Research Center IBM SP-2parallel computer in terms ofmillions of points updated persecond by the flow solver. Theproblem is that of viscous flowaround an aircraft wing. A goodmeasure of the quality of a parallelprogram is its scalability, which isdefined as the improvement inperformance as more processorsare added to the computation. Thefigure indicates that, even for arelatively small grid of fixed size of200,000 points, the scalability isquite good (heavy dashed curve).Performance is even better if theproblem size is allowed to grow withthe number of processors employed(heavy solid curve). For reference,the ideal speedup curve (thin solidline) is also shown.

The second figure indicates theimprovement in performance ofusing the MPI-I/O library over that ofthe standard, nonparallel I/O libraryon the SP-2, where a gain of up to afactor of 30 in write speed can beobserved.

40 60 10080

Ideal speedup

Variable grid size

Fixed grid size

120200

1

2

3

4

0


Meg

apo

ints

/sec

Fig. 1. Millions of points updated per second on IBM SP-2.

Although RANS-MP primarilytargets cache-based systems thatmake up the bulk of the latest high-performance computing architec-tures, care has also been taken toprovide good performance on moretraditional computers such as theCray C90 and the NEC SX-4. There-

fore, the code must be written toallow efficient vectorization, themain source of performanceimprovement on such machines.When the wing problem is solved onthe C90, RANS-MP attains a respect-able 45% of the maximum possibleperformance of the machine.


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Measurements show that more than99% of all computational statementsare executed in vector mode.

Point of Contact: M. Yarrow(650) [email protected]

Parallel Tools for Paralleland Distributed ComputerSystemsD. DiNucci, M. Frumkin, R. Hood,H. Jin, L. Lopez, R. Papasin,C. Schulbach, J. Yan

Software tools have beendeveloped that accelerate thedevelopment of Grand ChallengeComputational Aeroscience applica-tions for massively parallel process-ing systems. These software toolsand associated research focus onareas critical to understanding andusing computer systems capable of

trillions of floating point operationsper second, including: (1) perfor-mance tuning, visualization, andanalysis; (2) parallel debugging; and(3) programming paradigms andenvironments.

In the first area, an integratedperformance-tuning environment isdeveloped around the AutomatedInstrumentation and MonitoringSystem (AIMS). (See the first figure.)AIMS is a software tool that auto-matically instruments parallelFORTRAN and C programs, moni-tors their execution on parallelarchitectures, and displays andanalyzes their performance.Dynamic variation of system param-eters and overall performance areautomatically captured duringexecution and subsequently dis-played on the color screen of aworkstation. A key feature of AIMS isthat it provides source-code click-back, allowing the user to relatetrace events with specific statementsin the application program. AIMSalso supports tracking and visualiza-tion of interprocessor data move-ments. In addition to providing traceinformation, AIMS has been used toinvestigate the possibility of regener-ating program trace information fromstatistics collected during programexecution.

The Numerical AerodynamicSimulation trace visualizer (NTV) is arelated tool that provides an alterna-tive to the visualization kernel (VK)of AIMS. Whereas VK providesdynamic visualization of programs,NTV provides static, zoomableviews. Another product, Ben, is alibrary of visualization routines thatcan be used to develop visualizationcapabilities in other software tools

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64

and products. AIMS is available forthe IBM SP-2 (message passinginterface (MPI)) and on workstationclusters (parallel vertical machine(PVM) and MPI). NTV supports AIMStraces as well as native traces fromthe IBM SP-2.

The second area involves thedevelopment of a debugger for useon parallel and distributed computersystems. The portable parallel/distributed debugger (p2d2) (see thesecond figure) is a system using aclient/server model that is portableacross target machines and commu-nication libraries. This system allowsthe architecture- and operatingsystem-dependent code to belocated in a server while the client-side code remains highly portable.It was designed with scalable user

Fig. 1. AIMS software toolkit for automatically instrumenting parallelprograms, monitoring their execution, and displaying and analyzing theirperformance.

Fig. 2. p2d2 being usedto debug the runningprogram mp_overflow.


65



interface elements in expectationthat users will want to debugcomputations involving many (16 to256) processes. p2d2 is currentlyavailable on the IBM SP-2 (for MPI).Development of support for PVMhas also been completed.

In the third area, programmingparadigms and environments, theCooperative Data Sharing System(CDS) has been developed toprovide an efficient, portable, andsimple system for creating processesand communicating between themin cluster, message-passing, andshared-memory environments. Thissetup allows the user to specify thesemantics required of each commu-nication so that it can execute withnear-optimal performance on anytarget architecture: shared-memory,message-passing, or cluster. TheCDS application user interfaceconsists of two layers: a kernellevel (CDS1), with objectives ofminimality, orthogonality, portabil-ity, efficiency, and utility; and a userlevel (CDS2) built upon CDS1, withthe sole objective of providing auseful user interface without interfer-ing with the desirable characteristicsof CDS1. CDS1 is available on SUNSolaris and Silicon Graphics Inc.Challenge Array systems.

Point of Contact: C. Schulbach(650) [email protected]

Numerical AerodynamicSimulation ParallelBenchmarks 2.2William Saphir,R. Van der Wijngaart,Alex Woo, Maurice Yarrow

The Numerical AerodynamicSimulation (NAS) Parallel Bench-marks 2.2 (NPB2.2) bring a new eraof integrity to the performanceclaims of the vendors of high-performance parallel computers.NASA is an immediate beneficiaryof these benchmark tools, as is thescientific and engineering commu-nity at large, since evaluation ofhigh-performance computers cannow be based on objective perfor-mance criteria rather than vendorhyperbole. The NPB2.2 also standout as excellent source code modelsfor the development of futureparallel versions of simulationprograms for the aerospace industry.

NPB2.2 consist of source codeversions of seven computationalfluid dynamics applications andkernels that were originally given as“paper and pencil” specifications. Intheir original form, they gained wideacceptance as measures of parallelcomputer performance, but vendorimplementations were machine-specific and proprietary. The currentsource code versions, however, havebeen specifically designed to run onmodern parallel computers thatsupport the commonly availablemessage passing interface (MPI).They are available from the WorldWide Web, and have been designedto be extremely easy to use. Datagenerated by these benchmarks arenow available for a wide variety ofparallel computers from numerous

vendors, and are readily viewable atthe NASA NPB Web site.

New to NPB2.2 are the ISinteger sort kernel and a vastlyimproved FT Fast Fourier Transformkernel. Unlike the other kernels thatmeasure floating-point performance,the IS code does integer operationsonly and measures raw processorpower. It also provides a strenuoustest of the speed of the communica-tion network of a modern parallelcomputer. The new FT program, nolonger limited to 128 processors, hashad its floating-point performanceimproved. The three applicationbenchmarks known as BT, LU, andSP solve equations of viscous flow,each with a different algorithm.The remaining two kernels solve amultigrid problem and a so-called“embarrassingly parallel” problem.The suite provides a comprehensivetest of the capabilities and relativeperformance level of a parallelcomputer, making the task ofassessing high-performance comput-ers for NASA laboratories easier thanever before.

Point of Contact: M. Yarrow(650) [email protected]’

Large-Scale ParallelSemiconductor SimulationSubhash Saini

At the present time, severaltechnologies are pressing thelimits of the semiconductor-basedcomputer industry, including the0.1-micron foreseeable limit of thephotolithography process, quantum


66

effects, heat dissipation, the skyrock-eting cost of manufacturing plants,and others. NASA requirements forhigh-performance computers aredifferent from those of mainstreamindustry. For many applications,such as the High-PerformanceComputing and Communication(HPCC) remote exploration andexperimentation (REE) project, NASArequires low-powered, ultracompact,high-performance computers that areresistant to radiation damage. By theyear 2010, many important futureNASA missions will rely on petaflopscomputer systems. Applications ofinterest to NASA that will most likelyrequire petaflops computing includemultidisciplinary optimization ofcommercial aircraft designs, propul-sion systems, large-eddy and thedirect numerical simulation ofturbulence; computation of the radarscatter signature of aircraft bodies;full-scale simulation of the Earth’s

strategy for implementing paralleladaptive unstructured-grid technol-ogy for semiconductor devicemodeling has been developed. Thisstrategy addresses the importantissues, such as load balancing. Alsostudied were the scaling propertiesof several algorithms, such as fastmultipole expansions (FME) todetermine the trade-off between FMEand long-range molecular dynamicsmethods in terms of computationalcost. Both these methods are used indevice modeling.

Point of Contact: S. Saini(650) [email protected]

REVOLUTIONARY TECHNOLOGY LEAPS/SUPERSONIC TECHNOLOGY

Nonlinear AerodynamicShape Optimization ofHigh-Speed ResearchConfigurationsSusan Cliff, James Reuther, Ray Hicks

The overall goal of this researchis to develop an aerodynamic shapeoptimization technique that is basedon nonlinear computational fluiddynamics (CFD) methods andcontrol theory techniques; eliminatesthe dependence on a large numberof CFD solutions; and can beeffectively used to optimize aero-dynamic shapes to yield superioraerodynamic performance. Insupport of the high-speed research(HSR) program, the specific objec-tive is to apply these methods to

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atmosphere and climate; and thedesign, manufacture, and operationof smart nanorobots for spaceexploration.

A roadmap for the high-performance computing industry hasbeen developed and is presented inthe figure. Current consensus is thatpetaflops computing systems will befeasible in 20 years using advancedsemiconductor technology. AmesResearch Center has instituted a newprogram in semiconductor processand device modeling to ensure thatNASA will be able to meet futurerequirements of petaflop computing.In spite of the seemingly obviousneed for highly parallel computingas a simulation and design tool inthis arena, so far any utilization ofparallel systems has been rare. Theprincipal impediments includeaccess to parallel testbeds, as well asthe availability of usable softwareand parallel computing expertise. A

REVOLUTIONARY TECHNOLOGY LEAPS/␣ ␣ SUPERSONIC TECHNOLOGY


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R E V O L U T I O N A R Y T E C H N O L O G Y L E A P S / S u p e r s o n i c T e c h n o l o g y

candidate configurations to assesstheir capabilities and simultaneouslyenhance the aerodynamic perfor-mance of the vehicle.

The aerodynamic design forsupersonic cruise of high-speedcommercial transport aircraft is anextremely difficult problem becauseof the complex flow fields and theneed to efficiently integrate themajor components of the vehicle(i.e., the fuselage, wing, and enginenacelles) while satisfying numerousstructural and operational con-straints. Past design efforts haverelied upon linear theory methods.Unfortunately, the near-fieldinteractions of the components arenonlinear and the use of lineartheory-based design methodsprovides only limited design guid-ance. Furthermore, the level ofcruise aerodynamic performanceachievable with linear designmethods is insufficient to ensure aneconomically viable configuration.

The role of CFD in the aero-space industry today is primarilythat of an analysis tool used in thefinal stages of the design process.Although this tool has proved verybeneficial, to make full use of thepower of CFD it must be incorpo-rated into the framework of anautomated design process. Pastefforts to accomplish this objectivehave proved extremely difficult forapplications involving complexaircraft configurations because of thecomputational expense associatedwith the thousands of CFD solutionsthat are required to gain an under-standing of aerodynamic designspace and its related optima.

Traditional aerodynamic shapeoptimization methods use finite

differences to obtain the necessarygradient of an aerodynamic objec-tive function (for example, drag) withrespect to the design variables. Thus,if N is the number of design vari-ables used for the shape design, thenN flow solutions are required toobtain the gradient during eachdesign cycle. Through the use ofcontrol theory-based methods, a setof adjoint equations are formulatedthat reduce the computationalrequirement down to the equivalentof two flow solutions, independentof the number of control variables.The result is a computational savingsof greater than an order of magni-tude. Furthermore, since the gradientcalculations are no longer depen-dent on the number of designvariables, the shape of complexconfigurations can be optimizedusing a large number of designvariables.

Using the nonlinear design/optimization code named SYN87and its predecessors OPT3D andOPT67, which combine Euler flowsolvers with constrained and uncon-strained numerical optimizationalgorithms, five successful aero-dynamic designs have been accom-plished. The first four designs havebeen validated through wind tunneltesting. The most recent applicationof this automated aerodynamicdesign process, which used SYN87and the adjoint gradient computa-tions, was focused on the Mach 2.4HSR Technology Concept Airplane(TCA). The cruise aerodynamicshape of this configuration (shown inthe figure (see Color Plate 14 in theAppendix)) was optimized to obtainthe minimum drag subject to a largespectrum of realistic geometry

constraints, including wing spardepth, wing leading edge bluntness,landing gear box size and location,fuel volume, passenger cabindimensions, and floor attitude. Theoptimization procedure used up to140 independent design variablesdistributed over the wing andfuselage and focused on wingthickness and camber and fuselagecamber and area distribution. Over200 design iterations were executedin the overall design process, andthey yielded very significant perfor-mance gains relative to the baseline.These performance gains werevalidated through numerous detailedEuler and Navier–Stokes analyses.Hardware is currently being fabri-cated for a wind-tunnel test toexperimentally validate the results.

This design/optimizationapproach represents some of the firstsuccessful attempts to use the powerof CFD as a true design tool appliedto complex aircraft configurationswith a large realistic spectrum ofconstraints. In addition, the largeperformance gains achieved clearlydemonstrate the advantage ofusing nonlinear design methods toenhance aerodynamic performance.

Point of Contact: D. Bencze(650) [email protected]

68

Surface OperationsBehavioral EvaluationInterim Testbed forHigh-Speed ResearchMary K. Kaiser

The eXternal Vision System(XVS) element of the high-speedresearch (HSR) program is examiningissues associated with building ahigh-speed civil transport (HSCT)with no forward-looking windows.Forward visibility would be providedby a synthetic vision system, gener-ally conceived as displaying visiblelight camera imagery with superim-posed symbology. This designconcept presents numerous engi-neering and human factors chal-lenges, including the adequacy ofthe XVS display for control, naviga-tion, and obstacle detection;integration of the XVS display withthe side windows (which are opti-cal); and crew coordination in anXVS-equipped flight deck.

Surface operations may presentparticular challenges to an XVS-equipped aircraft because vehiclecontrol is primarily vision-based(compared to many phases of flightin which the pilot relies heavily oninstrument information) and becauseartifacts such as sensor-offsetparallax become more severe whenthe aircraft is close to the ground.

To examine these surfaceoperations issues in a high-fidelitytestbed, the HSR program is con-structing a near-full-scale testbed,the Surface Operations ResearchEvaluation Vehicle (SOREV). TheSOREV is scheduled to be opera-tional in late FY97. In the interim,

Ames has worked with industrypartners at Boeing and Honeywell toequip a full-size Ford van (shown inthe figure) with an XVS systemlocated at a rear driver station. Therear station has two XVS displays(forward and inboard) and an opticalwindow with the visibility anglesspecified by the Reference H designof the HSCT. The cameras can bemounted at several locations on thevehicle, creating parallax similar tothat anticipated with aircraftmounted camera systems. Transportdelays in the camera/display systemcan be introduced, and the impacton driver control and situationalawareness can be examined.Although its overall fidelity issomewhat limited, the SOREV isproving to be a useful testbed for

“first looks” at critical human factorsissues associated with the XVS andsurface operations.

Point of Contact: M. Kaiser(650) [email protected]

Fig. 1. The SOREV. Externally mounted cameras feed the forward andinboard displays at the rear driver station. An outboard side window isconfigured to simulate the side window visibility planned for the HSCT.

R E V O L U T I O N A R Y T E C H N O L O G Y L E A P S / S u p e r s o n i c T e c h n o l o g y

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REVOLUTIONARY TECHNOLOGY LEAPS/ACCESS TO SPACE

Propulsion Checkout andControl SystemAnn Patterson-Hine

The Propulsion Checkout andControl System (PCCS) was part ofthe Integrated Propulsion Technol-ogy Demonstrator (IPTD) tasksupported by the X-33 program.The objective of the IPTD was topredict and evaluate potentialimprovements in ground and flightpropulsion-system operations inefforts to reduce turnaround timesand to cut cost-risk factors. The IPTDconsists of liquid-oxygen and liquid-hydrogen propulsion modules, aremote interface unit that is aprototype of Rockwell’s X-33Phase␣ II propulsion system avionics-to-control-center interface, and aprototype control center at MarshallSpace Flight Center’s (MSFC’s)Advanced Engine Test Facility.

The task, which was completedin FY96, achieved the following:(1)␣ on-board diagnostic/prognosticalgorithms for the propulsion systemof the Reusable Launch Vehiclewere demonstrated to be capable oftrending and analyzing a historicaldatabase; (2) playback of IPTD dataon valve actuations identified earlyperformance degradation of the12-inch prevalve in the mainpropulsion system that otherwisewould have been undetectable;(3)␣ the diagnostic/prognostic algo-rithms are the first known applica-tion of predictive Integrated Vehicle

Health Management to an opera-tional cryogenic testbed; and(4)␣ testability models developed byusing a software tool set fromQualTech Systems, Inc. were used inpositioning the IPTD sensors.

The design models were auto-matically converted to real-timecode that monitored sensor data andthat worked with the Langley smart-sensor routines to identify off-nominal conditions to the operator.This successfully demonstratedRockwell’s approach to reducingsoftware development costs byreusing design models and softwarefor operational vehicle code.

Point of Contact: A. Patterson-Hine(650) [email protected]

REVOLUTIONARY TECHNOLOGY LEAPS/␣ ␣ ACCESS TO SPACE

R E V O L U T I O N A R Y T E C H N O L O G Y L E A P S / A c c e s s t o S p a c e

70

Space Science Enterprise

71

O v e r v i e wNASA’s Space Science Enter-

prise seeks answers to fundamentalquestions about the origin of theUniverse, the origin and evolution ofgalaxies and planetary systems, theorigin and distribution of life in theUniverse, and the connectionsbetween the Sun, Earth, and helio-sphere. Through our primary missionin astrobiology (the study of theliving Universe), Ames providespioneering research, technologydevelopment, and flight projects thatpromote fundamental discoveriesabout the origin, evolution, anddistribution of life within the contextof cosmic processes. Research isconducted to:

␣ ␣ •␣ ␣ Determine the abundance anddistribution of biogenic com-pounds that are conducive tothe origin of life

␣ ␣ •␣ ␣ Identify locations in the SolarSystem where conditionsconducive to life have existed

␣ ␣ •␣ ␣ Survey and begin surfaceexplorations of the most fasci-nating and accessible planetarybodies

␣ ␣ •␣ ␣ Discover the origin, evolution,and fate of the Universe, galax-ies, stars, and planets

␣ ␣ •␣ ␣ Survey cosmic rays and interstel-lar gas as samples of extrasolarmatter

␣ ␣ •␣ ␣ Explore the frontiers of theheliosphere

␣ ␣ •␣ ␣ Search for planets and planetaryformation around other stars

Exobiology and AstrobiologyAmes has been recognized as a

world leader in astrobiology andexobiology (search for extraterrestrial

life) since the inception of thesedisciplines. Research at Amesfocuses on revealing how life begins,on what processes govern its evolu-tion, on what destiny may berealized, and on how often life mayhave emerged on other planets.When coupled with Ames’ pioneer-ing research on the dynamics ofgalaxies, molecular gases andclouds, planetary systems, and theSolar System, our study of life isfacilitated by understanding thecosmic environment within whichlife evolves. Ames conducts studiesof biologically important materials ingeologic samples and in extrasolarmatter; provides theoretical insightsfor addressing major issues in life’sevolution; plays a key role asNASA’s expert in matters of plan-etary protection; and helps to focusthe science for future Mars missionson issues related to the possibility ofthe independent origin of life onMars.

One of the most importantquestions in exobiology and astrobi-ology is how living systems emergefrom molecular chaos. Highlightedin this report are exobiologicalsimulations that revealed severalnew and important basic principlesgoverning the ability of peptides toacquire ordered structures, to self-catalyze, and to give rise to a simplemechanism for transmitting signalsfrom the external environment to theinterior of a protocell.

The role of comets in the originof life is also featured. Comets,which can be considered the fossilsof the protoplanetary nebularprocesses, retain within their icynuclei clues about the beginning ofthe Solar System. Ames reported animportant finding this year on the

S P A C E S C I E N C E E N T E R P R I S E

72

composition and properties ofinterstellar and cometary ices thatmay have profound implications forour understanding of the originof life.

PlanetologyAmes conceived and initiated

7␣ of the 11 planetary missions thathave flown since 1972, includingthe Mars Pathfinder. The Galileoprobe made history on December 7,1995, with its entry into the atmo-sphere of Jupiter, the first time aspacecraft entered the atmosphereof an outer planet. Plunging intoJupiter’s swirling storm clouds at106,000 miles per hour, the probedescended 400 miles throughturbulence, violent winds, andclouds, transmitting data for almostan hour before the communicationssystem succumbed to the intenseJovian environment. Results from theprobe’s descent are reported below.

Ames also recently completed acomprehensive study of the SolarSystem which fully models the entirerange of bombardment, transport,and mixing effects by which highlyabsorbing “primitive” interplanetarymaterial pollutes, and redistributesmaterial in, an initially pristine icysystem such as Saturn’s rings.Surprising findings are described inthis report.

Of all the planets in the SolarSystem, Mars is most like Earth,especially in that its weather andclimate are dynamically similar toEarth’s and in that its history mayhave included life. Research high-lighted in this report includes anew finding on the structure of theMartian regolith and its role in theMartian climate; the results of Amesresearch on the nature of the Martian

oxidants—a primary obstacle touncovering the biological history ofMars; and a unique concept, thePascal Mission, to use Mars as anatural laboratory for the study offactors that control a planet’s climatesystem.

AstrophysicsAs NASA’s lead Center in

airborne astronomy, Ames pioneeredand developed astrophysics and hasthe world’s only capability formaking astronomical observationsfrom the stratosphere. Developmentwas begun this year on the Strato-spheric Observatory for InfraredAstronomy (SOFIA), the infraredtelescope of which will gatheralmost an order of magnitude morelight than its predecessor andachieve a five-order-of-magnitudeimprovement in capability. Amesastronomers, who also contributedirectly to space-based infraredscience, won the right to the mostobservation time on the premierinfrared space mission of thedecade—the European InfraredSpace Observatory. These and thehighlights described below arepresented more fully in later sectionsof this report.

Ames and the University ofTokyo produced the Mid-InfraredSpectrometer on the JapaneseInfrared Telescope mission whichobtained infrared spectra of morethan 10,000 objects and has yieldedinteresting new information on thecharacter of the interstellar material.Results obtained this year confirmthat two types of interstellar mate-rial—grains and certain polycyclicaromatic hydrocarbons (PAHs)—aremixed in a constant ratio throughoutdifferent interstellar regions of the

Galaxy, hinting at common evolu-tionary processes. A complementaryAmes study on PAHs revealed that anew type of PAHs, hydrogen PAHs(H-PAHs), found at the boundary ofthe Orion Nebula and OrionMolecular Cloud, are absent inhigher-radiation environments.Results presented in this reportindicate that different chemicallyactive regions in planetary nebulaeand molecular clouds are defined—at least in part—by the characteris-tics of the radiation environment.

Protoplanetary nebulae, thebirthplaces of planets and planetarysystems, are distributed throughoutthe Universe. The “primary accre-tion” process—the process by whichthe first sizeable objects (comets,asteroids, etc.) formed from solidsthat entered a given protoplanetarynebula as micron-sized dust motes—is one of the major unsolved prob-lems of the origin of planetarysystems. A new insight, achievedthis year upon completion of a newmodel of turbulence and dampingby particles in the midplane of aprotoplanetary nebula, challengescertain theories of accretiondynamics.

Ames researchers recentlycompleted the most comprehensivetheoretical computation of thepotential energy surface and dipolemoment for hot water in sunspotsof the Sun and in the spectra ofselected cool stars, revealing thatsunspot atmospheres are muchcooler in the shallow layers than hadbeen predicted by previous models.These results and other potentialapplications of the model arehighlighted in this report.

The final stages in the life of astar somewhat more massive than

73

the Sun was studied by Amesresearchers and colleagues from the University of Hawaii and theUniversity of Wyoming. The resultsprovide an important insight intounderstanding how the structuralevolution of the nebula, throughinteracting winds, might provide theconditions necessary for molecularsurvival.

Also described in this issue is aremarkable “hands-on” educationalsoftware package developed byAmes that allows students of all agesto perform simulated observations ofplanets around other stars, as if theywere the astronomers, and then toanalyze the data to determine thehabitable properties of the planets.Included in the package is a descrip-tion of Ames’ proposed Keplermission, the only currently practicalmethod for finding Earth-sizedplanets around other stars.

Space TechnologiesTo support the Space Science

Enterprise, Ames scientists andengineers develop, validate, andverify enabling, cutting-edge, high-payoff technologies for conductingfuture space science and explorationmissions at substantially reducedcosts. Cost reduction is achievedprincipally by using informationtechnology to develop advancedflight- and ground-system autonomytechnologies. The following high-lights are reported more fully in latersections.

An executive system for intelli-gent autonomous spacecraft,planned for the Deep Space Onemission, was prototyped this year.Deep Space One will autonomouslynavigate to asteroids and comets andwill be able to achieve its mission in

the face of a wide variety of faults,including total loss of command andcontrol from Earth.

Live tests of a key component ofthe Automatic Telescope Projectwere successfully completed. Theprimary objective is to provideadvanced scheduling and automa-tion infrastructure so that thebenefits and performance of single-user automatic telescopes can bemade available to a large commu-nity of users, with no additionalpeople in the loop. The benefits willbe a dramatic reduction in telescopeoperating costs and an increase inboth scientific productivity and easeof use.

Ames’ Assisted Space SystemExperimental Testbed (ASSET)project is an Internet-based globalspacecraft control network thatprovides operational support of avariety of low-cost missions and ahigh-risk, low-inertia testbed forvalidating spacecraft autonomystrategies. This year ASSET enabledrapid experimentation with revolu-tionary autonomy technologies in areal-world, complex space systemin support of the New Millenniumprogram concerning the datadistribution, principal investigatorinterfacing, beacon operations,ground-system automation, and faultmanagement.

Ames has developed WaveLab,a powerful suite of wavelet algo-rithms that can be used to character-ize the physical processesunderlying complicated temporaland spatial variations, removingunwanted observational noise fromdata, compressing data with insig-nificant loss of information, andprobing computer models forphysical processes with large


dynamic range. WaveLab is avail-able at no cost to the public on aWorld Wide Web site maintained atStanford University.

Significant progress has beenmade in understanding and improv-ing the operation of two of the maincomponents of a pulse-tubecryocooler for use in spacecraft. Inaddition, Ames developed a starsensor that can be mounted in acryogenic vacuum vessel to serve asa guide star-tracker for the GravityProbe B relativity mission.

74 P R O G R E S S I N E X O B I O L O G Y

PROGRESS IN EXOBIOLOGY

Remote Analysis ofMartian Surface MaterialsD. Blake, P. Sarrazin, D. Bish,D. Vaniman, S. Chipera, S. A. Collins,T. Elliott

A miniaturized x-ray diffractionand x-ray fluorescence (XRD/XRF)instrument for exploring the Marssurface is being developed; theinstrument will minimize theuncertainties inherent in remotemineralogical and geochemicalanalyses. The instrument has beennamed CHEMIN, in reference to itsrole as a simultaneous chemical andmineralogical analyzer. A function-ing prototype of this instrument usesa copper X-ray tube, transmissiongeometry, and an energy-selectivecharge-coupled device (CCD)operating in single-photon countingmode to collect simultaneous XRFand XRD data.

The ultimate use of this instru-ment will be in obtaining combinedXRD and XRF data from planetarysamples. Such an approach willgreatly improve the accuracy ofremote petrological analyses byconstraining the number of possiblemineralogic interpretations of thedata. For example, although theViking landers provided very usefulXRF data on the Martian regolith, thecomplex chemistry reported (particu-larly the mixed-anion suite thatincludes sulfur and chlorine, as wellas oxygen) allows a wide range ofmineralogic interpretations. Sinceremote XRF has yielded provenresults, the focus is on preliminarytests in obtaining quantitative

XRD data from the prototypeCHEMIN instrument.

X-ray diffraction is the mostdirect and accurate analyticalmethod for determining the presenceof mineral species, because the dataobtained by this method are funda-mentally linked to crystal structure.Other methods, based on chemicalor spectral properties, are derivativeand subject to much greater uncer-tainties. Moreover, significantprogress has been made in the lastdecade in the development ofquantitative XRD of multicomponent mixtures.

The Rietveld method, which fitsthe entire observed diffractionpattern with a pattern calculatedusing the crystal structures of theconstituent phases of the modelmineral system, shows great promisefor mineral analysis. This methodcan provide rapid quantitativeestimates of mineral abundance, aswell as compositional, unit-cellparameter and structural data onindividual minerals. In addition,recent advances in quadratic goalprogramming allow solution ofsimultaneous linear equations using

Fig. 1. Two-dimensional image of basalt diffraction pattern obtained withthe CHEMIN instrument using only monoenergetic copper-characteristicradiation. The rings correspond to lattice spacings within individual mineralsmaking up the basalt.

PROGRESS IN EXOBIOLOGY

75


chemical and mineralogic data. Useof these techniques with combinedbulk-sample XRD and XRF datamakes possible extraction of consid-erable information on individualmineral compositions.

To test the capabilities ofCHEMIN against realistically com-plex samples, Rietveld analysis wasused to determine mineral abun-dances from CHEMIN-deriveddiffraction patterns of a basalt. Thissample was chosen as representativeof a rock type that is known to beabundant on the Martian surface,and also one that fits the genericmineralogy of all of the Marsmeteorites identified so far (includ-ing the ALH84001 meteorite pur-ported to contain evidence ofprimitive Martian bacteria).

XRD and XRF data wereobtained from a sample of terrestrialbasalt with the prototype CHEMINinstrument using repetitive30-second counts. After accumula-tion of numerous 30-second-countdatasets, the data were analyzed ona pixel-by-pixel basis. X-ray powderdiffraction rings were generated by

plotting the two-dimensionaldistribution of those pixels contain-ing copper-characteristic radiation(first figure). The powder rings werethen integrated to generate conven-tional 2θ-versus-intensity powder-diffraction patterns (2θ is the anglebetween the diffracted beam and theentering beam). The resulting XRDdata were used as input to Rietveldrefinements. The results of theanalysis are shown in the table andin the second figure. Despite thecomplexity of the basalt sample andthe significant limitations of theprototype CHEMIN instrument, theRietveld analysis is surprisinglygood, with a calculated pattern that

agrees well with the observedpattern. In addition, the resultingmineral analysis agrees well withoptically determined modes for thissample. This level of success hasonly recently been obtained, andconsiderable improvement in theCHEMIN results are anticipated inthe near future.

The CHEMIN instrument hasbeen proposed for a number ofspace missions, and an XRD/XRFcapability is included in instrumentsuites proposed for Mars landers androvers by several working groups.

Point of Contact: D. Blake(650) [email protected]

P R O G R E S S I N E X O B I O L O G Y

Table 1. Rietveld quantitativeanalysis of basalt sample

Mineral Weight, %

Forsterite 7.5

Albite 28.9

Anorthite 17.5

Augite 4.7

Magnetite 1.9

Phlogopite 0.1

Florapatite 1.6

Sanidine 37.9

Fig. 2. Rietveld refinement of the diffractogram obtained by summing x-rayintensities shown in Fig. 1 radially around the central beam. The patterns areevaluated by least-squares fitting between model and actual results.

20 24 28

Background

Observed patternCalculated pattern

Difference pattern

32 36 40 44 4816128

1200

1600

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2400

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3200

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Stable IsotopeBiogeochemistry ofHydrothermal SystemsDavid J. Des Marais

Hydrothermal systems probablyexisted in any rocky planet whichwas sufficiently large to accumulatesubstantial internal heat fromradioactive decay and which alsopossessed a significant crustalinventory of water. Hydrothermalsystems provide the liquid water,nutrients, reduced conditions, andchemical energy necessary tosupport life. Therefore NASA’sastrobiology and solar systemexploration programs should includea search for hydrothermal systems inother planets.

The stable isotopic compositionof the elements oxygen (O), hydro-gen (H), sulfur (S), and carbon (C) inminerals and other chemical speciescan indicate the existence, extent,conditions, and processes (includingbiological activity) of hydrothermalsystems. The reactions between hotwater and rock-forming mineralsallow the isotopic ratios 18O/16O ofdeuterium to hydrogen (D/H) of theminerals to equilibrate with thiswater, causing isotopic changeswhich can be used to detect fossilsystems and to delineate their arealextent. These isotopic changes canindicate fluid composition, alterationtemperatures, water-rock ratios, andso forth. The 18O/16O values ofhydrothermal silica and carbonate

deposits tend to increase withdeclining temperature and thushelp to map temperature gradientswithin hydrothermal systems. The13C/12C values of carbonates and13C-depleted microbial organiccarbon increase along the thermalgradients of thermal spring outflows,principally because of the outgassingof relatively 13C-depleted carbondioxide (CO2). Hydrothermal waterscan differ in their D/H contentsbecause of their variety of sources,which can include seawater orrainwater, which falls over ranges inelevation and geographic location.Therefore, measurements of D/Hvalues in hydrothermal minerals canhelp to decipher the origins of thefluids. The 34S/32S and 13C/12Cvalues of fluids and minerals reflectthe origin of the S and C, the partialpressure of O2, and also the natureof key oxidation-reduction pro-cesses. For example, a wide rangeof 34S/32S values is consistent withequilibration below 100°C betweensulfide- and sulfate-bearing minerals,and can be attributed to sulfurmetabolizing bacteria and not tononbiological processes. Dependingon its magnitude, the difference inthe 13C/12C value between carbon-ate minerals and coexisting organiccarbon can be attributed either toequilibrium at hydrothermal tem-peratures or, if the difference in theratio exceeds 1%, to organic biosyn-thesis (see figure).

The observations of hydrother-mal mineral assemblages andcoexisting organic carbon inYellowstone National Park indicatethat both temperature gradients andmicrobial communities can indeedbe documented through measure-ments of their oxygen and carbon

Fig. 1. Carbon isotopic composition of crustal carbon reservoirs, withspecial emphasis on hydrothermal systems. The horizontal axis depictsvariations in 13C/12C values in parts per thousand, with lower values to theleft. Boxes and arrows depict carbon reservoirs and processes linking thereservoirs, respectively. The isotopic composition of hydrothermal carbonspecies can be affected both by mantle carbon and by contamination fromcrustal sources of organic and carbonate carbon.

+100–10

δ13C

–20–30

Subduction

Subduction

Biosynthesis

Decomposition

Weathering

Out-gassing

BurialDecomposition and burial

–40

Mantlecarbon

Fresh organic matter

Hydrothermalreduced carbon

HydrothermalCO2 and carbonate

MarineHCO3

–

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CO2:

Sea, Atm.

Sedimentary organic matter


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isotopic compositions. Parallelmeasurements are now beingmade in rocks from an ancient(400-million-year-old) hydrothermalsystem in Queensland, Australia.

Point of Contact: D. Des Marais(650) [email protected]

Fossilization Processes inThermal SpringsJack Farmer, Sherry Cady,David J. Des Marais

Stromatolites are laminatedbiosedimentary structures that formwhen communities of microorgan-isms either entrap sedimentarygrains, or induce the precipitation ofminerals through their metabolicprocesses. Fossil stromatolitesprovide a primary source of informa-tion about the early biosphere onEarth, and have also been identifiedas important targets in the explora-tion for a fossil record on Mars.These megascopic biosedimentarystructures are rich storehouses ofpaleobiological information andoften contain not only the fossilizedremains of the microorganismswhich produced them, but alsobiochemical and isotopic signaturesthat directly link them to lifeprocesses.

Thermal springs are highlyproductive microbial factories thatprovide an important glimpse intothe nature of the primitive biosphere.In recent years, the microbialcommunities and stromatolites ofthermal springs have assumed aprominent place in studies ofprimitive biospheres. During the

early history of Earth, it is likely thathydrothermal systems were wide-spread owing to higher internal heatflow, and to the thermal energyinvested by large impacts. Thus,hydrothermal environments areregarded as key environments for theorigin and early evolution of terres-trial life, a view that also receivessupport from the universal tree of lifederived by comparing the nucleicacid base sequences in the RNA ofliving organisms. The patterns ofearly branching suggest that thecommon ancestor of all livingorganisms was an extreme thermo-phile, that is, a microorganism thatpreferred living at temperaturesabove 80°C (176°F).

The fossil record of thermal-spring deposits is virtually unknown,and no subaerial systems have yetbeen recognized in the ancientgeological record of Earth. In order

to create a framework for recogniz-ing such deposits in the Precambrianrecord, the authors have beencarrying out studies of modernthermal-spring systems inYellowstone National Park, alongwith ancient deposits from localitiesin western North America andAustralia.

In FY96 studies of modernthermal springs led to severaldiscoveries that have helped refinethe understanding of stromatolitemorphogenesis and fossilizationprocesses at high temperatures.Columnar geyserites (see first figure),are high-temperature subaerialsplash deposits that form around thevents of siliceous thermal springs.The structures thus formed resemblemany Precambrian stromatolites.Columnar geyserites were firststudied in the late 1970s anddetermined to be abiogenic (that is,

Fig. 1. Thin-section view of columnar stromatolites (geyserites) formedaround high-temperature vents of silica-depositing springs in YellowstoneNational Park; columns are about 3 mm high.


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not produced by living organisms).Since that time, some authors havequestioned the biogenicity of theoldest fossil stromatolites, suggestingthat they were also formed inorgani-cally. But studies of modern geyser-ites have shown conclusively thatthese deposits are actually formed inthe presence of thin biofilms ofthermophylic bacteria and archae-bacteria, and that the geyseritemicrostructure reflects a significantbiogenic contribution.

In FY96 the first detailed paleon-tological studies of ancient subaerialthermal-spring deposits in northeastQueensland, Australia, were alsocompleted. These 350-million-year-old deposits are precise analogs forthe modern subaerial systems thathave been studied in Yellowstone.

Observations were made of theprimary biofabrics and microfossilsthat are preserved in these ancientdeposits, despite extensive texturalreorganization during diagenesis(second figure).

Point of Contact: J. Farmer(650) [email protected]

Molecular Biomarkers forStromatolite-BuildingCyanobacteriaLinda L. Jahnke, Roger E. Summons,Harold P. Klein

Life began on early Earth in anenvironment devoid of free molecu-lar oxygen (O2). It is clear that therise of O2 as a consequence of theevolution of oxygenic photosynthesishad a profound effect not only onthe subsequent progression ofbiological evolution but also onEarth’s geological history. Althoughoxygenic photosynthesis evolvedwithin the cyanobacterial lineage,evidence for this event’s timingremains obscured within themolecular and rock records. Onepotential help in resolving this issueresides in the complex organicmolecules that can be extracted fromancient sedimentary rocks. Thesemolecules, called biomarkers, arethe remnants or molecular fossils ofancient microorganisms. The carbonskeletons of such fossil moleculescan survive structurally intact forbillions of years, and organicgeochemists are working to identifythem in ancient organic sedimentarymaterials. The challenge is tounderstand the link between suchmolecular fossils and their “living”counterparts, the biomarker mol-ecules synthesized by contemporarybacterial groups. Understanding thefunction and influence of environ-mental factors on the synthesis ofsuch biomarker molecules in thesource organism can then provide abasis for interpretation of this ancientorganic record.

Fig. 2. Thin-section view of fossilized microbes from 350-million-year-oldsiliceous thermal-spring deposits discovered in the Drummond Basin ofnortheast Queensland, Australia; individual filaments are about 20 µm indiameter.


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Extant cyanobacteria are adiverse group of prokaryotic micro-organisms found in a wide variety ofmodern environments. We havefocused our study on the types ofcyanobacteria involved in theconstruction of microbial mats andtheir fossilized equivalents, stroma-tolites. These laminated, organo-sedimentary structures are amongthe most common fossils in thegeological record. Importantbiomarkers for identification ofcyanobacterial input to sedimentaryorganic matter are a group ofstraight-chain hydrocarbons(alkanes) having 17 to 20 carbons(C17-C20) with midchain,branched methyl groups such as7-methylheptadecane (C17). Thesemethylalkanes are specific to

cyanobacteria, are resistant tobiodegradation, and form some ofthe oldest known biomarkers, havingbeen isolated from Proterozoic rocksdated at 1.7 billion years ago. Morerecently, we have identified anotherclass of methylated alkane havingtwo methyl branches at carbons 7,11or 7,10 in a cyanobacterium,Phormidium luridum. We found thatthese dimethylheptadecanes (DMA)were only synthesized when thecyanobacterium was grown with lowlevels of dissolved inorganic carbon(DIC). Cells grown with DIC levelsequivalent to atmospheric levels ofcarbon dioxide (CO2) (0.03%)contain DMA, whereas cells grownwith 1% CO2 have only a straight-chain n-heptadecane. We havecarried out a screening of a variety

of cyanobacteria to determine theextent to which this low DIC-DMAsynthesis phenomenon occurs. Todate, we have screened 6␣ marineand 12 freshwater strains ofcyanobacteria. None of the marinecyanobacteria, including severalSynechococcus, three Oscillatoria,and a Pseudanabaena were able tosynthesize DMA. This was also truefor a variety of cyanobacteria(Gloeocapsa, Synechococcus,Oscillatoria, Pseudanabaena)isolated from the hot spring, micro-bial mats in Yellowstone NationalPark. Two other Yellowstoneisolates, Chlorogloeopsis andFischerella, did synthesizedimethylalkanes, but these com-pounds differed in carbon chainlength and methyl group positions,and were synthesized under bothhigh and low DIC conditions. Theonly cyanobacteria found to becapable of dimetylheptadecanesynthesis were four Phormidiumtypes isolated from siliceous hotsprings (see first figure). LikePhormidium luridum, theYellowstone Phormidium containedhigh levels of DMA when grownunder low DIC conditions.

The Phormidium are responsiblefor the formation of a type of colum-nar stromatolite, the Conophytons(conical-formed microfossils).Conophytons were one of the mostdistinctive groups of stromatoliteswhich disappeared near the end ofthe Precambrian. The Phormidiummats in Yellowstone provide asurviving “primitive” analog for

Fig. 1. Photomicrograph of a Phormidium (filament width 1.5 µm) isolatedfrom a Yellowstone microbial mat.


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study of the Conophytons (secondfigure). DMA are found only inPrecambrian oils, and disappearfrom younger organic sediments justas the Conophyton stromatolitesdisappear from the rock record. Theenvironmental factors controllingdimethylalkane synthesis in the

Yellowstone Phormidium mats mayprovide important insights forinterpretation of the organic molecu-lar fossil record.

Point of Contact: L. Jahnke(650) [email protected]

Earth-Threatening CometsLeave Tell-Tale Dust TrailsPeter Jenniskens, David Morrison

Over its geologic history, Earthhas been bombarded by a continu-ous shower of large asteroids andcomets, some of which led to large-scale extinctions. Unlike otherdangers, impacts of larger bodiescan affect mankind as a whole andpose a threat to modern civilization.The first step toward avoiding suchimpacts is to know where thepotential impacting objects are. Mostlarge asteroids can be found bydedicated searches using largetelescopes, because they have ashort orbital period and come closeto Earth frequently enough to bedetected. However, that is not thecase for comets with long orbitalperiods, which come back to theinner parts of the solar system onlyonce every 200–100,000 years. Andsome 2 to 10% of all such impactsare thought to be due to these long-period comets.

Researchers are studying thepossibility of using the meteoroidparticles in the path of these cometsas a means of detecting their pres-ence. From numerous accounts ofamateur observers, they know thatsome meteor streams show briefepisodes of high activity: the meteoroutbursts. At such times, Earthcrosses relatively recent ejecta ofparticles, which evaporate in Earth’satmosphere in the flashes of lightthat are called meteors. Mostintriguing are the outbursts thatoccur at times unrelated to the returnof the comet to perihelion, and it is

Fig. 2. Silicifying Phormidium mat (width 12 inches) showing Conophytonstructure, Weeds Pool, Yellowstone National Park.


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suspected that these might beassociated with long-period comets.It remained unclear whether theoutbursts were caused by a trail ofdust in the path of these comets orby clouds of dust in orbits with ashorter orbital period. No observa-tions made with standard meteorobserving techniques had beensuccessful, until FY96.

It was proposed that the plan-etary motions affect the orbits ofparticles, causing Earth to periodi-cally traverse the trail of dust. Thereturn of one such stream in Novem-ber of 1995 was predicted. Condi-tions would be favorable to measurethe orbital period of the particlesover Europe and Africa, where it wasnight at the expected time of theevent, and the point from which themeteors radiated would be high inthe sky, allowing good viewing. Anetwork of photographic and image-intensified TV systems was set up inAndalusia, Spain, operated princi-pally by amateur observers of theDutch Meteor Society.

The outburst did indeed occurand was confirmed by many observ-ers in Europe. Meteor rates increasedbriefly to five meteors per minute.Most of the meteors were too weakto be photographed. A rare colorimage is shown in the figure (seeColor Plate 15 in the Appendix). Tenmeteors were recorded from mul-tiple sites and triangulation of theirpaths allowed the reconstruction ofthe orbit of the particles. Theparticles had a long orbital period,confirming that this meteor outburstwas due to a trail of dust in the wakeof a long-period comet. Identifica-tion was made of 14 such streamsthat produce occasional outbursts

and techniques are being developedto find more in order to study theirproperties.

Point of Contact: P. Jenniskens(650) [email protected]

Capturing Cosmic Duston MirKenji Nishioka, Ted Bunch,Mark Fonda, Glenn Carle,Sherwood Chang, James Ryder,Janet Borg

As part of exobiology’s effort tosolve the quintessential question ofhow life started on Earth, it isnecessary to have informationconcerning the prehistoric origin andevolution of biogenic elements andcompounds from the interstellarmedium that coalesced into the solarsystem. Interplanetary and cosmicdust particles (IDPs/CDPs) arebelieved to have survived from thatearly period largely unchanged; as aresult, they may shed light on thechemical pathways taken by thebiogenic elements and their com-pounds in moving from their originsin stars and the surrounding mediato their incorporation into planetarybodies such as Earth. Thus theinterest to capture contamination-free cosmic dust particles.

Ames Research Center, the SETIInstitute, and Lockheed MartinMissiles and Space have developedultrapure aerogel, containing aboutone part per million carbon, forcontamination-free capture of CDPsin Earth orbit. This group joined withthe University of Paris’s Institute for

Astrophysical Studies and flew aCDP-capture experiment early thisyear (October 1995 to February1996) as part of the EuropeanExposure Facility’s Comrade experi-ment on the Russian Mir spacestation. Two small capture cells/modules each 9 by 5 by 1.5 centi-meters thick were flown, recovered,and returned to Ames on March 25,1996. One of the two aerogelcapture modules was exposed fromearly October 1995 until earlyFebruary 1996; the second capturemodule was exposed for only10␣ days during the Orionids showerin October 1995. These capture cellswere the first aerogel experiments tofly on Mir. The results of preliminaryanalyses of the capture modules aresummarized below. Strict proce-dures were followed in handling themodules to ensure that any changesdetected, including contamination,would be a result of the environmentaround Mir, from shipping of themodules (packing material), or fromcaptured particles.

Physical (visual) examinationsof the modules were done in a10,000 class clean room. When themodule covers were removed, theintegrity of the module/aerogel wasverified; it had survived shipping,launch, orbital exposure, andrecovery without apparent structuralproblems, except for stretching ofthe platinum retainer wires. Thisprobably resulted when entrained airin the aerogel could not escapequickly enough to equalize theinternal pressure and the rapidlydecreasing external pressure duringlaunch, thus causing the aerogel tobulge and the wires to stretch. Thecosmetic surface blemishes on the


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aerogel surface reported in the 1995Research and Technology Report,appeared noticeably darker androugher, whereas the clear unblem-ished surfaces appeared unaffectedin the recovered modules; this waslater confirmed by microscopicexamination. These initially blem-ished areas are probably susceptibleto ozone oxidation.

While in the clean room, surfaceand subsurface aerogel sampleswere taken from the modules foranalyses. Organic chemical analysesof the aerogel surface samplesshowed high contamination levels(2%) of dioctyl adipate, a plasticizer.This was unanticipated, and thereare no reports of this contaminant asan orbital experiment concern in theliterature. Additional samplings fromthe modules confirmed the highcontamination levels. Interiorsamples showed that the contamina-tion did not migrate and was con-fined to the surface.

An automated microscopicscanning system at the University ofCalifornia at Berkeley was used toscan the modules for impacts.Several candidate impact points withtracks were found and are beinganalyzed by an x-ray probe tech-nique at Brookhaven NationalLaboratory. Preliminary x-rayfluorescence spectra results from thex-ray probe of a track failed to detectparticulate matter at the end of thetrack. But, the “chondritic” elementscalcium (Ca), iron (Fe), nickel (Ni),manganese (Mn), titanium (Ti), andchromium (Cr) were found in thetrack and could indicate the breakupof a pyroxene particle; however,small amounts of lead (Pb), zinc(Zn), copper (Cu), strontium (Sr), andzirconium (Zr) were also found,

strongly suggesting the possibility ofan orbital debris particle or othersource of contamination.

Valuable insights were gainedinto the manufacturing, fabrication,and use of aerogel for building asuccessful IDP/CDP capture instru-ment from this flight experiment.Aerogel is robust and holds togethereven under IDP/CDP impact, andunder launch and ground handlingloads. Also, aerogel does not appearsusceptible to the migration ofsurface contaminants. But asexpected, the experiments gave riseto new questions. For example,where did the high concentrationof dioctyl adipate come from? Doparticles, especially at the micron ortens of micron size, survive capture,and how will these micron-sizeparticles and their tracks be foundand analyzed cost effectively?

Point of Contact: K. Nishioka(650) [email protected]

Simple Peptides atWater-MembraneInterfacesAndrew Pohorille, Christophe Chipot

Even the simplest protocell musthave had the capability to catalyzethe chemical reactions needed for itssurvival and growth and to commu-nicate with its environment. Thesefunctions must have been accom-plished by simple molecules thatcould have been present in aprotobiological milieu. One suchgroup of potential early catalysts andsignaling molecules were the

peptides—possible precursors ofenzymes and receptors. Unfortu-nately, short peptides typically havedisordered structures in aqueoussolution and, therefore, do notappear to be suitable for the desiredcellular functions. However, atwater-membrane, water-oil, orwater-air interfaces, many of thesepeptides, depending on theirsequence, can acquire a broad rangeof well-defined secondary structures,such as a-helix, b-strand, or b-turn.A crucial, common characteristic ofthese interfaces is that a nonpolarphase is adjacent to water.

The ability of small peptides toorganize at aqueous interfaces wasexamined by performing a series oflarge-scale molecular dynamicscomputer simulations of severalpeptides. The peptides were com-posed of two amino acids, nonpolarleucine (L) and polar glutamine (Q),in a variety of environments; theydiffered in the size and sequence ofthe amino acids. Among the mol-ecules studied were the dipeptidesLL, LQ, QL, and QQ. Although thesepeptides were too short to form asecondary structure, they are verygood models for use in examiningthe conformational preferences ofthe peptide backbone as a functionof the sequence and the environ-ment. The studies of L/Q peptideswere extended to include twoheptamers, of sequence LQQLLQLand LQLQLQL. The sequences weredesigned to maximize the interfacialstability of the a-helix and b-strandconformations, respectively, byexposing polar side chains to waterand nonpolar side chains to anonpolar phase.

Finally, a transition of anundecamer (11 residues), composed


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entirely of leucine residues, from adisordered structure in water to ana-helix in a nonpolar phase, repre-senting the interior of the membrane,was investigated. This is the first timethat the complete folding of apeptide in solution was accom-plished in computer simulations.

The simulations revealed severalbasic principles governing thesequence-dependent organization ofpeptides at interfaces. Understandingthese principles allows for determin-ing how peptides could haveperformed protocellular functions.

Short peptides tend to accumu-late at interfaces and acquireordered structures, provided thatthey have a proper sequence ofpolar and nonpolar amino acids.The specific identity of amino acidsappears to be less important, whichis a desirable protobiologicalproperty. The dominant factordetermining the interfacial structureof peptides is the hydrophobic effect,which is manifested at aqueousinterfaces as a tendency for polarand nonpolar groups of the solute tosegregate into the aqueous andnonpolar phases, respectively. Theresulting structures are calledamphiphilic. Exceptions from thistendency are observed only whenintramolecular hydrogen bonds areformed in the nonpolar phasewithout completely removing polarside chains from water, a uniquefeature of interfacial systems.

Based on the results for foldingthe LQQLLQL heptamer to ana-helix at the water surface, it isproposed that, whenever possible,peptides fold at interfaces through aseries of amphiphilic intermediates.Transitions between these intermedi-ates involve changes not only in

backbone angles but also in confor-mations of side chains. Once folded,the peptides form structures that aresuitable for polymerization and havethe potential for catalytic activity.

If peptides consist of nonpolarresidues only, they insert into the

nonpolar phase. As demonstrated bythe example of the leucineundecamer, such peptides fold intoan a-helix as they partition into thenonpolar medium (see the twofigures). The folding proceeds

Fig. 1. Polyleucine undecamer interacting with the water-hexane interfaceat t = 0 nanoseconds. The center of mass of the peptide is locatedapproximately 11 angstroms from the water-hexane interface. In water, thestructure of the peptide is disordered. The atoms of the polyleucine are darkgray, the oxygen and hydrogen atoms of water are medium gray and white,respectively, and the CH2 and CH3 segments of hexane are light gray.


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through an intermediate conforma-tion, called a 310-helix, whichremains in equilibrium with thea-helix. Once in the nonpolarenvironment, the peptides canreadily change their orientation withrespect to the interface from parallel

to perpendicular, especially inresponse to local electric fields.The ability of nonpolar peptides tomodify both their structure andorientation with changing externalconditions may have provided a

simple mechanism for transmittingsignals from the environment to theinterior of a protocell.

Point of Contact: A. Pohorille(650) [email protected]

Silicon-MicromachinedGas ChromatographySystemThomas Shen, James Suminto,Frank Yang, Daniel Kojiro,Glenn Carle

The development of gas chro-matographic equipment for plan-etary atmospheric probes and soilgas or pyrolytic analysis was re-quired for both the Viking mission toMars and the Pioneer Venus mission.A gas chromatography (GC) instru-ment was used for the Pioneer Venusmission. However, future missions,such as the Mars Exploration Mis-sions and missions to probe theatmospheres or moons of the outerplanet, will require further reduc-tions in equipment weight, volume,and power requirements.

NASA is in a very dynamicmode at this time. A massive effort isunder way to revolutionize thetechnical approach to spacecraft androbotic exploration. The DiscoveryProgram is the first of these newapproaches. Other programs follow-ing it include New Millennium,Micro-spacecraft, and Nanoinstru-ments. All of these enterprises havein common the requirement forbetter, faster, cheaper. Clearly,current technology will not likely befeasible for future space studies.

Fig. 2. Polyleucine undecamer interacting with the water-hexane interfaceat t = 40.2 nanoseconds. The peptide has folded into an a-helix, and thepeptide backbone vector makes an angle of about 20° with the normal tothe water-hexane interface. The color scheme is the same as describedin Fig. 1.


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A silicon-micromachined GCsystem in which the detector andcolumn are integrated into a smallpiece of silicon has been studied byseveral researchers. The problem isthat no sensitive detector has beendesigned and tested. A proposal wasmade to use the matastable ioniza-tion detector principle, and replacethe radioactive material with theglow discharge method, which hasnot been studied on the silicon-micromachined GC system. A verynarrow discharge distance can beproduced and controlled, a heliumionization detector can be produced,and a highly sensitive analysis canbe obtained (concentrations belowthe parts-per-million level can bedetected) through a micromachinedsilicon wafer. In addition, a column

on the chip with the new in-house-developed highly efficient siliconpolymer material (U.S. patented) willbe modified and coated to separatemost chemical components. Thissmall and highly sensitive GC systemwill be able to meet future missionrequirements.

In this first year of the project,several micromachined chips withdifferent electrode designs wereprepared and tested. The preliminarydevices were produced by Micro-Tech Scientific Inc. Several chipshave been evaluated. The dischargecurves of these chips are demon-strated in the figure.

Point of Contact: T. Shen(650) [email protected]

Nitrogen Sources andSinks on Early EarthDavid P. Summers

One important form of fixed andreduced nitrogen on early Earth isammonia. However, currentgeochemical evidence points to anonreducing atmosphere whichcontains nitrogen (N2) instead ofammonia. One source of ammoniainvolves the formation of nitrite(NO3

–) which can then be reducedto ammonia by ferrous iron (Fe+2).It has also been suggested that thiscannot be an important source ofammonia since nitrite can react withammonia (to make nitrogen).

Whether this is true, however,depends on how the kinetics of thereactions involved compare with thespeed of other sources and sinks forboth ammonia and nitrite. If thereaction of nitrite with ammonia isslow compared with other processesthat make and destroy ammonia,then it will not be important. Anyevaluation of the importance ofvarious sources and sinks of nitriteand ammonia, and of whetherammonia is likely to be present insignificant amounts, requires ananalysis of all the kinetic processesaffecting those species.

Using a kinetic analysis of ratedata that had either been measuredat Ames or were already publishedin the literature, a kinetic analysiswas performed to establish what theconcentrations and rates might havebeen in the early ocean. Plausiblesinks/sources for nitrite and ammo-nia on early Earth are: the reductionof nitrite to ammonia, the reaction ofnitrite with ammonia, photochemi-cal destruction of either nitrite or

Fig. 1. Discharge curves of micromachined chips.

300 400 5002001000

.01

.02

.03

.04

0

Voltage (V)

Cu

rren

t (m

A)

Detector #4

Detector #5

Detector #6


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ammonia, and destruction at hydro-thermal vents. The photochemicaldestruction of nitrite depends ontrace species that can react withphoto-generated hydroxy radicalsand on the amount of ultravioletlight, neither of which is known forcertain to have existed on earlyEarth. Furthermore, the product ofphotolysis, nitric oxide (NO), is thesame compound that nitrite (andhence ammonia) is formed from.Therefore, values for rates of photo-chemical destruction probablyrepresent only an upper limit.Ammonia can also be lost byadsorption into clays. However, thiswill be significant only when theammonium concentration is highenough to compete with potassiumand serves mostly to limit theconcentration below an upper limitof 10 millimolar.

Under most conditions, theprimary sink for nitrite is reductionto ammonia. Destruction at hydro-thermal vents is important at acidicpH’s and close to the freezing pointof water. The reaction betweenammonia and nitrite is not animportant sink for either nitrite orammonia. Photochemical destruc-tion, even in a worst case scenario,is unimportant under many condi-tions but could be important underacidic, high carbon dioxide (CO2)pressure, or low-temperatureconditions. The primary sink forammonia is photochemical destruc-tion in the atmosphere. Under acidicconditions, more of the ammonia istied up as ammonium (reducing itsvapor pressure), and hydrothermaldestruction becomes more impor-tant. At 25°C, pH 7.6, and 0.2␣ atmo-sphere of CO2, nitrite and ammoniahave steady-state concentrations of

3␣ x 10–8 and 2 x 10–6 molar, respec-tively. The very low nitrite concen-tration reflects the fact that the nitriteis reduced to ammonia before it hasa chance to build up or undergo anycompeting processes. The concen-tration is such that its importance formany processes envisioned for theorigin of life (like the formation ofamino acids) is unclear.

This is part of a broader questionof whether life would have startedin the open ocean, where dilutionmakes the formation of morecomplex species difficult, or some-where where a means of concentra-tion species (such as with vesiclesor by evaporation) is present. Ingeneral, concentration would tend toraise the concentration of all species,rather than change the relativeimportance of the source and sinks(except where species are notallowed to be photolyzed or sweptinto hydrothermal systems).

Point of Contact: D. Summers(650) [email protected]

Progress in Planetary Systems

Planetary RingsJeff Cuzzi

Planetary ring and moonsystems, especially the magnificentSaturn system, contain elements ofprocesses in particle disks thatprovide insights into planetaryformation. Saturn’s rings will be amain focus of study for the Cassinimission, to be launched in October1997. Interplanetary meteoroids

bombard planetary rings, generatingejecta which transport mass andangular momentum in systematicways throughout the system. Anexhaustive study, which fully modelsthe entire range of bombardment,transport, and mixing effects bywhich highly absorbing “primitive”interplanetary material pollutes andredistributes material in an initiallypristine icy system such as Saturn’srings, has been completed. Thestudy includes careful treatment ofthe fate of ejecta particles as they flyabout within a realistic radial profileof ring particle abundance, and alsodetailed radiative transfer modeling,using actual material refractiveindices of the individual ring particlereflectivity as a function of wave-length and location in the rings.

The model implies (1) that withmost parameters of the modelconstrained by other observations,it is found that the basic globalbrightness and color differencesbetween the major ring regions(A-ring, B-ring, C-ring, etc.) can beunderstood for the first time, and in asimple way, by differential darkeningcaused by the infall of spectrallyneutral, highly absorptive, probablycarbonaceous, meteoritic materialwith orbits much like those ofcomets; (2) that the “initial,” primor-dial composition of the rings isalmost entirely water ice, but mustcontain a uniformly distributed,highly red, probably organic mate-rial such as is found in “primitive”bodies in the outer solar system andin Titan’s organic atmospheric haze(silicates are not acceptable ascoloring agents); (3) that the radialprofile of ring particle color (andthus compositional) variationsprovides a good fit to the model

PROGRESS IN PLANETARY SYSTEMS


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profiles for a range of exposuretimes which is in agreement withexposure-time estimates frombombardment effects on radialvariations of ring structure; and(4)␣ that nominal parameters for themodel imply a ring age of the orderof 100 million to 1 billion years,depending on the ejecta yield andthe meteoroid flux, indicating thatthe rings may not be as old as thesolar system (4.5 billion years).

Point of Contact: J. Cuzzi(650) [email protected]

Planetesimal Formation inthe Protoplanetary NebulaJeff Cuzzi

The “primary accretion”process—the process by which thefirst sizable objects (comets, aster-oids, etc.) formed from solids thatentered the protoplanetary nebula asmicron-sized dust motes—is one ofthe major unsolved problems inunderstanding the origin of planetarysystems. One key accomplishmentthis year was the completion of anew model of self-consistent turbu-lence generation and damping, bythin, dense layers of large (10-cmradius and larger) particles in themidplane of a protoplanetarynebula. Prior studies neglected therole of the particles in dampingturbulence in the gas; a scheme toaccount for this effect has beendeveloped and implemented. Thescheme begins with the Reynolds-averaged equation for the turbulentkinetic energy. The full two-phase

equations are averaged, and newterms appear as a result of particledamping, which has been modeledusing a gradient-diffusion-typeapproach.

In FY96, several differentparameterizations for dissipation ofturbulence by the gas itself, whichhas a major effect, were compared.A two-length scale model, a law-of-the-wall model, and two variableeddy-frequency models wereexplored; few really significantdifferences in model behavior werefound between these parameteriza-tions. Significant damping of nebulaturbulence does occur, to a degreethat is particle-size dependent, butthe damping effect is not sufficientlystrong to allow the particle layer tosettle into a gravitationally unstabledense midplane layer as some priorworkers had speculated. Thisappears to be one of the first fullycoupled, physically parameterizedstudies of turbulence damping bymass loading—certainly this is so inthe context of an orbiting disk.

Three-dimensional directnumerical simulations of particles inturbulence have been exhaustivelyanalyzed. The Taylor microscaleReynolds number ranges from 40 to140, and the code handles onemillion particles at each of 16 Stokesnumbers (the Stokes number is theratio of particle stopping time toKolmogorov eddy turnover time).Previously, it was demonstrated thatthe particle size most stronglyconcentrated (by orders of magni-tude) is in good agreement withchondritic meteoritic data. This year,it has been demonstrated for the firsttime that the particle density field forthe most strongly concentratedparticle size is a multifractal—and

that a certain key descriptor of themultifractal (the so-called singularityspectrum) is Reynolds-numberindependent.

Quantitatively, the density-fieldsingularity spectrum agrees with thatfor turbulent dissipation, perhapsproviding some profound cluestoward explaining this very impor-tant process. It is now feasible tomake use of extensive mathematicaltechniques developed for fractalanalysis to predict the probabilitydensity of particle concentration atarbitrary Reynolds numbers,strengthening the applicability ofthese results to plausible nebulaewith Reynolds numbers that areorders of magnitude higher than areachievable numerically.

Point of Contact: J. Cuzzi(650) [email protected]

PASCAL: A Mars ClimateNetwork MissionRobert M. Haberle, David C. Catling,Steven C. Merrihew

Of all the planets in the solarsystem, Mars is most like Earth. Inparticular, its weather and climateare dynamically similar to Earth’s.Mars therefore offers a naturallaboratory for the study of the factorsthat control a planet’s climatesystem. Yet the kind of observationsthat are needed to carry out such astudy, namely long-term simulta-neous measurements from a networkof globally distributed surfacestations, are lacking in NASA’s Marsexploration program. To remedy

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this, a Mars climate network missionwas proposed in response to the 5thAnnouncement of Opportunity toNASA’s Discovery Program. Thismission was named PASCAL afterthe 17th century French scientistwhose name is synonymous withthe Système International unit ofpressure.

Pressure is the key measurementof the PASCAL mission. It provides ameasure of the total mass in acolumn of air. Given information onits horizontal and temporal variationone can infer the nature of theplanet’s general atmospheric circula-tion and climate system. Fortunately,pressure is also easy to measure, andpressure sensors do not requireorientation or deployment. Thus,very simple landers can be designedthat are light and robust. In effect,we are trading off the ability to makemany different kinds of measure-ments at a few sites, for just a fewmeasurements at many sites. Thistrade allows us to achieve the globalcoverage that is required to observethe planet’s climate system whilekeeping the total mission cost wellwithin the Discovery cap.

PASCAL’s mission objective is toestablish a network of 24 globallydistributed surface stations that willmeasure hourly variations in pres-sure and temperature over a periodof 10 Mars years (~18.8 Earth years).This long-term continuous presencewill define the nature and variabilityof the planet’s climate system ontime scales ranging from hours toyears. It will also provide a weathermonitoring infrastructure for futureMars missions. In addition tonetwork science, PASCAL will gatherdata on the structure of the atmo-sphere as each probe descends to

the surface. This aspect of themission will be particularly valuablefor future Mars orbiters which planto aerobrake into their final orbits.

PASCAL would be launched inApril of 2001 and arrive at Mars inJanuary 2002. The 6.8-kilogramprobes would be released from aspin-stabilized carrier on directapproach to Mars. To achieve globalcoverage, the probes would bereleased in salvos of eight, eachseparated by a propulsive time-of-arrival adjustment to allow Mars torotate underneath. Entry descent andlanding would utilize a heat shield, aparachute, and crushable materialfor final deceleration. One possiblenetwork configuration resulting fromthis deployment scheme is shown inthe figure (see Color Plate 16 in theAppendix).

To ensure long lifetimes, each ofPASCAL’s surface stations would bepowered by a Light Weight Radio-isotope Heating Unit (LWRHU)coupled to a thermoelectric con-verter. The LWRHU also providesthermal control for the surfacestations. Communication wouldoccur through one of the orbiters ofthe Mars Surveyor Program (MSP).MSP plans to have orbiters at Marsbeginning in September 1997 andcontinuing well into the nextcentury. As a safety precaution,however, PASCAL’s landers arecapable of storing up to 5 Mars yearsof data should an orbiter not beavailable.

Point of Contact: R. Haberle(650) [email protected]

The Center for StarFormationD. Hollenbach, P. Cassen

The Center for Star FormationStudies, a consortium of scientistsfrom the Space Science Division atAmes and the astronomy depart-ments of the Universities of Califor-nia at Berkeley and Santa Cruz,conducts a coordinated programof theoretical research on star andplanet formation. The Centersupports postdoctoral fellows, seniorvisitors, and students; meets regu-larly at Ames to exchange ideas andto present informal seminars oncurrent research; hosts visits ofoutside scientists; and conducts aweek-long workshop on selectedaspects of star and planet formationeach summer.

The Star Formation SummerWorkshop in 1996 was held atWellesley College in Wellesley,Massachusetts, and included, inaddition to the Ames scientists,about 100 astrophysicists from allover the world.

The main focus of work in FY96was on the collapse of dense cloudsto form protostars with protoplane-tary disks, the evolution of thesedisks, which ultimately form planets,and the influence of young massivestars on the surrounding star-formingmolecular cloud. D. Hollenbach,A.␣ Tielens, and M. Kaufman mod-eled the thermal structure andspectra of dense molecular cloudswhich are collapsing to form highmass stars. A similar calculation wasmade by C. Ceccarelli (University ofGrenoble), D. Hollenbach, andA.␣ Tielens for clouds collapsing toform low-mass stars. When the


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model spectra are compared withobservations, observers can identifycollapsing clouds and measure therate at which the protostellar mass isincreasing. D. Hollenbach andD.␣ Neufeld (Johns Hopkins Univer-sity) calculated the heating andionization created when the collaps-ing cloud hits the protoplanetarydisk. Comparisons of the modelswith recent radio observations ofhot, ionized gas surrounding anearby protostar made it possible todetermine the rate of mass accretiononto the disk and the mass of thecentral protostar. K. Chick andP.␣ Cassen developed models toexplain the survival of presolarmaterial during the formation of thesolar system, as dust particles in thecollapsing molecular cloud eventu-ally incorporate into primitivemeteorites.

Once formed in the collapse,protoplanetary disks around solar-type stars evolve for millions of yearsas they form planets. K. R. Bell andP. Cassen examined the shapes ofprotoplanetary disks and demon-strated how the temperature depen-dence of the effective grain opacitycan lead to configurations in whichmuch of the disk is shadowed fromthe central star. B. Pickett, P. Cassen,and R. Durisen (Indiana University)used three-dimensional hydrody-namic simulations to show how thedevelopment of gravitational insta-bilities in the early stages of proto-planetary disks is controlled by theradiant energy losses.

Young massive stars radiatecopious amounts of ultravioletradiation, which heats, dissociates,and ionizes the surrounding molecu-lar cloud, and which ultimatelyleads to the dispersal of the cloud

and the cessation of star formationin the cloud. D. Hollenbach andH.␣ Stoerzer modeled these pro-cesses, incorporating a largenumerical code which followedthe time-dependent chemistry, thethermal balance, and the transport ofradiation. Their models predict theinfrared spectra from such regions,so that observations can be inter-preted quantitatively in terms of therates of these destructive processes.

These theoretical models havebeen used to interpret observationaldata from such NASA facilities as theInfrared Telescope Facility, theKuiper Airborne Observatory, andthe Infrared Astronomical Observa-tory, as well as data from numerousground-based radio and opticaltelescopes. In addition, they havebeen used to determine require-ments for future missions such asthe Stratospheric Observatory forInfrared Astronomy and the pro-posed Space Infrared TelescopeFacility.

Point of Contact: D. Hollenbach(650) [email protected]

Energetic TrappedParticles near JupiterJohn D. Mihalov

On December 7, 1995, theGalileo Probe carried experimentsinto Jupiter’s atmosphere, near theplanet’s equator. The experimentcomplement included an energetic-particle telescope supplied by agroup at the University in Kiel, WestGermany. Data from this experimentcould improve earlier measurements

of the innermost Jovian energetictrapped proton fluxes, made with thePioneer 10 and 11 spacecraft, aswell as provide data from the regioneven closer to the planet that hadnot yet been directly traversed byspacecraft. Beginning at 3 hoursbefore atmospheric entry, inside theorbit of Io, and until entry, theexperiment sampled the energetictrapped particle environment. Fluxmeasurements and energy spectraland angular distribution data forenergetic electrons and protons wereobtained.

The electron fluxes appear tobe within a factor of 3 of valuesobtained by earlier experimentsaboard Pioneers 10 and 11, atlocations where comparisons couldbe made. Except nearest to theatmosphere, where the energyspectrum steepened considerably,the most probable measured elec-tron energy was about 20 and40␣ million electron volts, respec-tively, for each of two separateelectron-energy thresholds, basedprincipally on energy-dependentresponses for the experimentdeduced from Monte Carlo simula-tions. Energetic-proton fluxes,spectra, and angular distributionswere measured in three separateenergy ranges in the 42 to~131 million electron-volt energyrange. The proton fluxes wereobserved to decrease abruptlyinward from the location of Jupiter’sring, and also as Jupiter’s atmo-sphere was approached.

Future analyses of the decreasesin particle fluxes measured as theatmosphere was approached maygive insight into the structure ofJupiter’s near-equatorial upper


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atmosphere, because the energeticparticles lose energy as they interactwith atmospheric constituents whilethey drift around the planet andbounce along the magnetic field. Inaddition, atmospheric interactions ofthe electrons are characterized byCoulomb scattering that causesdiffusion of mirror points alongmagnetic field lines. Some energetictrapped helium, in the 62 to136␣ million electron-volt pernucleon energy range, evidently wasdetected outside Jupiter’s ring.

Point of Contact: J. Mihalov(650) [email protected]

Wavelet SoftwareJeff Scargle

Wavelets are a mathematicaltool for the analyzing and interpret-ing time series, images, and otherdatasets. New wavelet-basedmethods, developed for scientificand engineering applications, areuseful for the following: (1) Charac-terizing the physical processesunderlying complicated temporaland spatial variations; (2) removingunwanted observational noise fromdata; (3) compressing data with onlyinsignificant loss of information;(4)␣ probing computer models forphysical processes that have a largedynamic range.

A powerful suite of waveletalgorithms to implement all theseideas has been developed and madepublicly available under the name“WaveLab.” WaveLab was a coop-erative research project between

NASA Ames Research Center andthe Statistics Department of StanfordUniversity through Joint ResearchInterchanges, and was funded by theNASA Astrophysics Data Programand Astrophysics Software andResearch Aids Program. The authorcollaborated with David Donohoof the Stanford and U.C. BerkeleyStatistics Departments on thisproject. The actual software is in theform of MatLab (copyright theMathWorks, Inc.) scripts, which canbe easily translated to other systems.

The World Wide Web site,maintained at Stanford (http://playfair.Stanford.EDU:80/~wavelab/)includes downloadable software forUnix, Macintosh, and Windowscomputers, complete documenta-tion, tutorials in basic and advancedwavelet transform methods, sampledata, and browser routines forexploring the sample data.

The WaveLab system has beendownloaded by several thousandpersons who have registered theiruse of this free, public-domainsoftware, many of whom haveindicated that they have alreadyfound WaveLab useful for theirresearch, teaching, or commercialenterprises. The developers answerquestions and help with userproblems by e-mail.

Point of Contact: J. Scargle(650) [email protected]

Time-DependentStructures in GalaxiesBruce F. Smith, Richard A. Gerber,Richard H. Miller,Thomas Y. Steiman-Cameron

Numerical experiments onmodels of galaxies are yielding newinsights into galactic structures anddynamics. This research is designedto examine time dependencies in thestructural components of galaxiesand to determine the implications forboth the structural and dynamicalevolution of galaxies. The results ofthese investigations are being usedin interpreting and understandinghigh-resolution observations ofgalaxies made by the Hubble SpaceTelescope (HST) and other advancedobservational programs. A series ofnumerical experiments has beenmade on the Cray C90 and parallelmachines at the Numerical Aerody-namic Simulation (NAS) Facility atAmes Research Center to understandthe nature of time-dependentprocesses in galaxies. These experi-ments probed the nature of complexmotions observed at the centers ofgalaxies including those seen at thecenter of our Galaxy.

Global oscillatory modes havealso been seen in the numericalexperiments. These n-body experi-ments provided the first experimen-tal evidence of long-lived globaloscillatory motions in sphericalsystems. These oscillations havebeen identified as normal modes;the entire galaxy rings like a bell.Several modes have been identified,but two are dominant and both arespherically symmetrical. The first isnearly a homologous contraction


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and expansion of the entire galaxy(the fundamental mode; a “breath-ing” mode), and the second has onenode. A detailed study of the effectsof softening in the representation ofthe potentials in the calculations hasverified the earlier results on long-lived global oscillations.

Given that the normal-modeoscillations persist over manydynamical time scales, a naturalquestion is: What processes couldgive rise to the oscillations? Amongthe possibilities are that (1) theoscillations could be left over fromthe galaxy formation process,(2)␣ they may be initiated by inter-actions with neighboring galaxies,or (3) they could grow frominstabilities.

These global oscillatory modesmay play an important role in thestructure and evolution of disk/halogalactic systems. The approach hasbeen to assume that a significantfraction of the mass in a galaxy is ina dark halo. The halo oscillates andthe luminous disk material respondsto these oscillations. In the numeri-cal experiments the disk respondsto the time-varying potential bydeveloping a ring structure thatforms and disappears during eachoscillation cycle (see first figure (seeColor Plate 17 in the Appendix)).This pattern of response persists overtime periods approaching a Hubbletime (assumed age of the Universesince the big bang). The responsecan be understood as a resonance ofthe stars in an annular region wherethe disk epicycle frequency is thesame as the halo oscillation fre-quency. This appearance of the ring,or annular gap, is reminiscent ofsome S0 galaxies (disk-like struc-tures), such as NGC 4513. Such

systems are not uncommon andmight be explained by the interac-tion of a disk with an oscillatinghalo. As the evolution proceeds abar develops in the inner disk (seesecond figure (see Color Plate 18in the Appendix)). Many galaxies,including our own, have bars in theircentral regions.

Point of Contact: B. Smith(650) [email protected]

Galileo EncountersJupiter: Results from theProbeRichard E. Young

The cone-shaped Galileo probeentered the atmosphere of Jupiter onDecember 7, 1995, at a speed ofover 106,000 miles per hour andsurvived deceleration forces of228␣ times Earth’s gravity. Afterdeploying a parachute, it relayeddata to the Galileo orbiter space-craft, which was overhead, for57.6␣ minutes. At the same time, theGalileo orbiter began a 2-year,11-orbit tour of Jupiter. So far it hashad close flybys of the Galileanmoons Ganymede, Callisto, andEuropa. The images it provides havespatial resolutions 10–100 timesbetter than the Voyager images.

The Galileo probe project ismanaged by NASA Ames ResearchCenter. Hughes Space and Commu-nications Co., El Segundo, Califor-nia, designed and built the probe.Lockheed Martin HypersonicSystems (formerly General Electric),

Philadelphia, Pennsylvania, builtthe probe’s heat shield. NASA’s JetPropulsion Laboratory, Pasadena,California, built the Galileo orbiterspacecraft and manages the overallmission.

The ratio of helium to hydrogenby mass is a key piece of informationin theories of planetary evolution.For the Sun, this value is about 25%.Comprehensive analysis of resultsfrom the probe’s helium-abundancedetector have shown that the heliumabundance for Jupiter is near 24%,about the value for the primordialSun.

The Jovian helium abundanceindicates that gravitational settling ofhelium toward the interior of Jupiterhas not occurred nearly as fast as itapparently has on Saturn, where theapproximate helium-to-hydrogenratio is just 6%. This indicates thatJupiter is much hotter in its interiorthan its neighbor Saturn, the nextlargest planet in the solar system. Italso may cause scientists to revisetheir estimates of the size of therocky core believed to exist deep inthe center of Jupiter.

The abundances of severalheavy elements, including carbon,nitrogen, and sulfur, are significantlygreater on Jupiter than on the Sun.This implies that the influx ofmeteorites and other small bodiesinto Jupiter over the eons since itsformation has played an importantrole in Jupiter’s evolution.

However, minimal complexorganic compounds were detected,indicating that such complexcombinations of carbon and hydro-gen are rare on Jupiter and that thechances of finding biological activitythere are extremely remote.


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The winds, determined fromtracking of the probe, persisted deepbelow the clouds, strongly suggest-ing that heat escaping from deep inthe planet’s interior drives the winds,rather than solar heating. Since allthe outer giant planets exhibit strongwinds, scientists hope that under-standing Jupiter’s winds will lead toimportant new insights into theirunusual meteorology.

The Galileo probe apparentlyentered Jupiter’s atmosphere nearthe southern edge of a so-calledinfrared hot spot, which is believedto be a region of reduced clouds.The probe’s nephelometer (aninstrument used to study suspendedparticles) observed only one distinctcloud layer, and that a tenuous oneby Earth standards. It is likely to bean ammonium hydrosulfide cloud.Three distinct cloud layers (an upperlayer of ammonia crystals, a middlelayer of ammonium hydrosulfide,and a thick bottom layer of waterand ice crystals) were expected.There were, however, some indica-tions from the probe net flux radiom-eter and nephelometer that theprobe started taking direct measure-ments in the bottom part of Jupiter’stop ammonia ice cloud layer.

Further analysis of probe datahas confirmed the preliminary reportthat the Jovian atmosphere appearsto be relatively dry, with much lesswater than anticipated on the basisof solar composition and on predic-tions from data sent by the Voyagerspacecraft that flew by Jupiter in1979. These studies predicted awater abundance for the planet oftwice the solar level (based on theSun’s oxygen content.) Actual probemeasurements now suggest an

amount of water much less than thatof the Sun.

The probe’s instruments foundmuch less lightning activity onJupiter per unit area than on Earth.Lightning on Jupiter was found to beabout one tenth of that found onEarth in an area of the same size.Although there is less lightningactivity, the individual lightningevents are, however, about 10 timesmore energetic than similar eventson Earth.

Point of Contact: R. Young(650) [email protected]

Regolith Effects on Mars’ClimateAaron Zent

In FY96, analysis of the adsorp-tion of water on Martian analogmaterials at Mars-like conditions wascompleted. In laboratory experi-ments, it was discovered that themass of adsorbed H2O was approxi-mately an order of magnitude lessthan previously predicted. Theseresults were used to derive newadsorption isotherms which reflectthe heterogeneity of the surface siteson Martian (or any) soil.

In collaboration with HowardHouben at Ames, these new iso-therms were applied to the study ofthe transport of water by the Martianatmosphere. It was found that thehorizontal advection of water bythe Martian atmosphere could notreproduce the observed patterns ofatmospheric H2O variations, but that

substantial vertical exchangebetween the atmosphere and theregolith could explain the results. Incollaboration with Bruce Jakosky atthe University of Colorado, it wasfound that nighttime inflections inthe atmospheric temperature recordat the Martian surface could beexplained by the condensation ofH2O in the atmosphere, at a frostpoint which supports the model ofdiurnal H2O exchange.

Point of Contact: A. Zent(650) [email protected]

The Nature of the MartianOxidantsAaron Zent

In FY96, laboratory analysis ofthe ability of hydrogen peroxide(H2O2), complexed by the Ti4+cation, was completed to reproducethe results of the Viking biologyexperiments. It was discovered thatthe results of the Labeled Releaseexperiment, in which organicmolecules were oxidized by atemperature-labile oxidant in thesoil, could be reproduced by outer-sphere (that is, with an interveninghydroxyl radical (OH) group)peroxo-Ti complexes. The ability ofinner-sphere (that is, no interveningOH group) complexed H2O2 toreproduce the Gas Exchange experi-mental reactivity and stability patternis still being investigated.

Also explored was the role ofthe diffusion of H2O2 into theMartian regolith, and the role of


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impact gardening in redistributingoxidized material through theMartian regolith. One finds that forreactive half-lives of the order of100,000 years, diffusion will carrythe oxidant into the upper 20 metersof the Martian regolith; also impactcratering will stir this materialthroughout the upper 100 meters ofthe regolith, necessitating deepdrilling if unoxidized material is tobe recovered.


A Thermo-AcousticOxidant SensorAaron Zent

In FY96, an investigation wasbegun into the feasibility of using athermo-acoustic oxidant sensor toidentify and quantify the nature ofatmospherically produced oxidantsin the Martian atmosphere. A seriesof selective chemical coatings,including lead sulfide, metal phtha-locyanines, and peroxidase areplaced on chemiresistors and surfaceacoustic-wave devices. The mode ofmeasurement for the chemiresistorsis resistivity change owing tobonding between the measure andthe coating; for the acoustic-wavedevices it is mass changes of thesame coating. Sensitivity to hydro-gen peroxide, ozone, and carbonmonoxide is demonstrated.

In collaboration with Dr. MarcMadou of the University of Califor-nia at Berkeley, flight electronics forthis experiment are being developed.In the coming year, the crosstalk and

effect of background gases on theproposed array of coatings will beinvestigated.


Progress in Astrophysics

Astrobiology in theAstrochemistry LaboratoryLouis J. Allamandola, Scott Sandford,Max Bernstein, Robert Walker,Dave Deamer

The Ames AstrochemistryLaboratory has made major contri-butions to the understanding of thecomposition and properties ofinterstellar and cometary ices. This isdone by studying laboratory analogsof cometary and interstellar ices. Animportant application of this work tothe origin of life is reported here.Since comets are considered to bea major source of the moleculesbrought onto primitive Earth beforelife began, their organic compositionis of central importance to questionsconcerning the origin of life.

Cosmic ices contain the verysimple molecules, water (H2O),methanol (CH3OH), carbon monox-ide (CO), carbon dioxide (CO2),molecular hydrogen (H2), ammonia(NH3), and formaldehyde (H2CO),as well as more complex species.Ultraviolet irradiation of these icesproduces other simple species suchas H2, H2CO, CO2, CO, methane(CH4), formyl radical (HCO), andmore complex organic moleculesknown as amides, nitriles, amines,

ketones, aldehydes, and polymerswhich are of particular interest froma prebiotic perspective. The readyformation of these complex organicspecies from simple starting mixturesand the ice chemistry that ensueswhen these ices are warmed suggestthat interstellar ices and comets mayhave played an important part in theorigin of life.

In addition to cometary icesraining a rich inventory of poten-tially important prebiotic moleculesdown onto early Earth, the com-pounds in cometary ices may alsohave played a role in early mem-brane production. Formation ofmembranes is considered a criticalstep in the origin of life, for they arerequired to isolate and protect theinterior workings of a cell from thesurrounding medium. Within theconfines of a membrane, conditionssuch as acidity can be moderatedand held at a different value fromthat in the surrounding medium,nutrients can be concentrated, andso on. Although it is uncertain wheremembrane formation falls in thesequence of events leading up to theorigin of life, it is considered anabsolutely crucial step. When themost complex organic moleculesproduced by irradiation of thesimple mixed molecular ices areplaced in water, water-insolubledroplets form naturally. This self-organizing, lipid-like behavior issimilar to that found for the organiccomponents of the Murchisonmeteorite. The figure shows micro-graphs of these nonpolar droplets.Both photographs are of the samefield of view, with the upper photo-graph taken in normal light (yellow-ish cast) and the lower in fluorescent

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emission stimulated by a black light(ultraviolet light). The upper photo-graph shows the presence of twodistinct phases, liquid water andinsoluble droplets. Several of theself-organized droplets show intrigu-ing structures suggestive of cellwalls. In comparing the upper andlower photographs, it is interesting tonote that all of the larger and manyof the smaller droplets have trappedblue photoluminescent material alsoproduced by the original ice irradia-tion. The ability to trap energyreceptors within these structures isalso considered a critical step in theorigin of life, for it provides themeans to “power” the protocell, asphotosynthesis does today in plants.

Point of Contact: L. Allamandola(650) [email protected]

Spectrum Synthesis of HotWater in Sunspots andSelected Cool StarsDuane F. Carbon, David Goorvitch

The objective of this research isto define the energy distribution oflate-type stars so that their physicalstate is better known. Better informa-tion about their physical state willthen lead to improved abundancedeterminations and energy stan-dards. Very recently, Partridge andSchwenke of Ames Research Centercompleted an elaborate theoreticalcomputation of the potential-energysurface and dipole moment functionfor H2O. They have used theirresults to predict the positions and

Fig. 1. Photomicrographs of the water-insoluble droplets formed when a fewdrops of water are placed on the most complex molecules produced byirradiation of an interstellar and cometary ice analog. Both photographsshow the same field of view, with the upper photograph taken in naturallighting and the lower in fluorescence stimulated by ultraviolet. Takentogether, these photographs show that the self-organizing droplets formnaturally from these materials and that they also trap luminescent materialsin their structures.


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strengths of nearly 308 million1H1H16O lines. This line tabulationis the most complete now available.It extends to sufficiently high excita-tions so that the spectra of M-stars(cool red stars) may be modeledwith greater accuracy than everbefore provided the predicted lineparameters of Partridge andSchwenke are themselves accurate.

Synthetic sunspot spectra havebeen computed using the Partridgeand Schwenke H2O line list and thesunspot umbral models. In order totest the new line list, a carefulcomparison of these syntheticspectra and of published high-resolution sunspot atlases has beencarried out. This comparison showsthat the new H2O line list success-fully predicts the sunspot H2Ospectrum and that it can specifywhere further improvements in theline tabulation are necessary. Inaddition, as part of this study, it isdemonstrated that sunspot atmo-spheres are much cooler in theirshallow layers than predicted by themodels and that the most recent linetabulation for the OH molecule isseriously in error.

Using the new H2O tabulation,the extent to which hot stellarwater blankets the H (1.65 microns),K␣ (2.20 microns), and L(3.45 microns) passbands forselected K- and M-star modelatmospheres and, thus, the energydistribution of these stars, is alsoinvestigated.

Point of Contact: D. Carbon(650) [email protected]


A High-Altitude SiteSurvey for SOFIAMichael R. Haas, Leonhard Pfister

The Stratospheric Observatoryfor Infrared Astronomy (SOFIA) willhave a 2.5-meter telescope mountedin the aft section of a Boeing 747 SPfor use in making astronomicalobservations at wavelengthsbetween 0.3 and 1600 microns.This study investigates the meteoro-logical conditions above 41,000 feetand finds that there are significantweather patterns at these altitudeswhich can adversely affect airborneastronomy.

Experience has shown that high-altitude cloud cover and water-vaporoverburden are the most importantmeteorological factors affecting thequality of astronomical observationsat typical flight altitudes. To deter-mine acceptable home base sites forSOFIA, these factors must be mea-sured over broad geographicregions, since a typical flightpathcovers hundreds of kilometers. Theonly source of such data is satelliteswhich provide global coverage ofEarth over an extended period oftime.

This study gathers the bestavailable satellite data, shows thatthey corroborate airborne experi-ence, and demonstrates that they areconsistent with well-known globalcirculation, convection patterns,and upper-tropospheric/lower-stratospheric dynamics. Part (a) ofthe figure (see Color Plate 19 in theAppendix) shows the total frequencyof cloud occurrence as measured bythe Stratospheric Aerosol and GasExperiment (SAGE II). This instru-ment uses a limb occultation

technique, so it has good verticalresolution, but relatively poorhorizontal resolution. The cloud-frequency data have been verticallyintegrated above 41,000 feet andaveraged over the three summermonths (June, July, and August) for a6-year period. Part (b) of the figureshows the total frequency of cloudoccurrence for summer as measuredby the High-Resolution InfraredRadiation Sounder (HIRS) sensors onpolar orbiting National Oceanic andAtmospheric Administration satel-lites since June, 1989. Since thissatellite is nadir-looking, this datasethas much better horizontal resolu-tion, but a significantly higherminimum optical depth and poorervertical resolution.

Water vapor is the principalmolecular absorber throughoutmuch of the infrared. Its strongvertical stratification at altitudesbelow the tropopause is one of theprimary motivations for conductingairborne observations from thestratosphere, where the water-vaporoverburden is relatively small andconstant. Furthermore, the negativetemperature gradients just belowthe tropopause allow rapid verticaltransport of moisture. When com-bined with low, upper tropospherictemperatures, this results in theformation of extended, thin sheetsof cirrus clouds. Part (c) shows theaverage tropopause height for thesummer season, and part (d) showsthe water-vapor overburdens inprecipitable microns as inferred fromthe Microwave Limb Sounder (MLS)for the summers of 1992 and 1993.Although the positive temperaturegradient above the tropopausestrongly increases the verticalstability of the atmosphere and

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places a lid on the rapid verticaltransport of moisture in Earth’satmosphere, there are clearly largevariations from this simple model.

The largest variations in high-altitude weather over the UnitedStates occur in the summer becausethe tropopause is near 41,000 feet.Moreover, different portions of theUnited States lie in different meteo-rological regimes in terms of large-scale circulation and the potentialfor convection. The eastern Pacific isdominated by the downward motionassociated with the mid-Pacificupper-level trough, and by generallylower sea surface temperatures. Eastof a line extending from northernMexico along the Rockies intoCanada, there is upward motionassociated with the continentalupper-level ridge. Warm moist airfrom the Gulf of Mexico, and to alesser extent from the Gulf ofCalifornia, promotes convection eastof the Rockies and in northwesternMexico. Moffett Field, the siteselected for SOFIA operations, iswell within the regime of downwardmotion which results in lower upper-level cloudiness and lower water-vapor overburdens.

Point of Contact: M. Haas(650) [email protected]

Kepler MissionEducational and PublicOutreach SoftwareDavid Koch

In response to the strategic goalsof finding other habitable planets

and conveying this objective tostudents and the public, an educa-tional software package has beendeveloped and distributed publicly.

Experience with educators hasshown a demand not just for infor-mation, but also for science data thatstudents could analyze. This hasbeen a difficult challenge, since ingeneral the latest data from airborneand space-borne experiments almostalways requires sophisticated dataprocessing and an “educated eye”to glean the subtle effects beingobserved. However, the observationsto be performed by the KeplerMission, which has been proposedto the Discovery Program, to detectEarth-sized planets are based on astraightforward principle that can beeasily understood even by upperelementary students. An interactivesoftware package has been devel-oped that allows the students to bothperform simulated observations as ifthey were the astronomers and thento analyze the data to determine thehabitable properties of the planet.

The Kepler Mission␣ has beenproposed as a Discovery Mission tosearch for habitable planets. Thepurpose of the mission is to continu-ously and simultaneously observe160,000 stars for evidence ofplanetary transits. When a planetpasses in front of its star it causes thestar to dim. When a second transit ofthe same duration and with the samebrightness change occurs, the exactorbital period can be predicted.When additional transits are seen,one has a high confidence that aplanet has been detected. From theperiod, the orbital distance of theplanet from its star can be calculatedand the characteristic temperatureof the planet estimated. From the

change in brightness the planet sizecan be calculated, and the mass andsurface gravity can be estimated.

The software package hasseveral components, including thefollowing:␣ ␣ 1.␣ ␣ A description of the latest resultsin the search for planets beyond ourown solar system;␣ ␣ 2.␣ ␣ A description of a habitableplanet, one where liquid water maybe found on the surface;␣ ␣ 3.␣ ␣ A description of the variousmethods, including the capabilitiesand limitations of the differentdetection techniques;␣ ␣ 4.␣ ␣ A description of the KeplerMission, the only currently practicalmethod for finding Earth-sizedplanets;␣ ␣ 5.␣ ␣ An interactive Kepler Missionsimulator;␣ ␣ 6.␣ ␣ A biography of Johannes Kepler,a description of his three laws ofplanetary motion, and informationon his life and times.

The software is written inHyperstudio™ for the Macintosh,and the Hyperstudio™ player isincluded. The software can bedownloaded from the Kepler Missionweb site (WWW.kepler.arc.nasa.gov).When compressed, the entiresoftware package with the player is1␣ megabyte and will fit on a singlehigh-density disk; thus it is easy forteachers to copy it and carry it intothe classroom. Use of the softwaredoes not require an Internetconnection.

Point of Contact: D. Koch(650) [email protected]


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Mid-Infrared Studies ofDiffuse InterstellarMaterialThomas L. Roellig

Infrared observations of theemission from material located inthe diffuse regions of space betweenthe stars can provide importantinformation on its composition andenergy state. This information iscrucial to our understanding of starformation and galactic evolution.Unfortunately, such observations arevery difficult, largely because thisemission is very weak and is easilydrowned out by infrared radiationemitted from the telescope optics.Furthermore, many of the mostinteresting regions in the infraredspectrum are obscured by absorptionin Earth’s atmosphere.

As a result, a telescope in spacecooled to temperatures only a fewdegrees above absolute zero isneeded for these investigations. Sucha telescope, optimized for infraredstudies of diffuse regions, was flownin 1995 in a NASA/Japanese SpaceAgency collaboration—the InfraredTelescope in Space (IRTS) infraredsurvey mission. The Mid-InfraredSpectrometer (MIRS), an instrumentdeveloped and operated jointly byNASA Ames and the University ofTokyo, was attached to the IRTS andoperated over wavelengths rangingfrom 4.6 to 11.7 microns. This is anideal spectral region for investiga-tions of infrared emission from solidmaterial, since it covers many of thediagnostic stretching and bendingmodes of candidate interstellarmaterial. The IRTS/MIRS telescope/instrument combination achieved

sensitivities that were orders ofmagnitude better than any instru-mentation previously used for diffusemid-infrared emission studies.

The first data from the MIRShave now been analyzed and haveyielded interesting new informationabout the interstellar material. Theobserved mid-infrared interstellaremission was found to be concen-trated almost solely in a few emis-sion bands (see the figure). This was

true both for those regions locatedwithin the plane of the galaxy andfor those regions above the galacticplane. The remarkable similarity ofthe spectra from the different regionsindicates that there is little chemicaldifferentiation between theseregions. The spectral featuresthemselves are indicative of emis-sion from a class of hydrocarbons—polycyclic aromatic hydrocarbons(PAHs). In the scenario envisaged to

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Fig. 1. Spectra obtained from the Mid-Infrared Spectrometer on the InfraredTelescope in Space mission. For all spectra, the galactic longitude wasapproximately 50°. The different lines correspond to different galacticlatitudes, b. The solid line indicates emission from -0° 40’ < b < 0°, thedashed line emission from 1° < b <2°, the dotted line emission from2° < b < 3°, and the dot-dashed line emission from 3° < b < 5°.


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operate in the interstellar medium,these molecules absorb ultravioletphotons and then emit this energy inthe infrared. The spectra obtained bythe MIRS show that the mid-infraredemission from the diffuse regions inthe galaxy can be attributed almostsolely to this material. The MIRSdata also show that the previouslyunexplained excess emissionobserved in the mid-infrared by theearlier Infrared Astronomical Satel-lite (IRAS) mission can be attributedto these emission bands.

Interestingly enough, a compari-son of the spatial distribution ofthese mid-infrared emission featureswith the emission at the muchlonger wavelength of 100 micronsobserved with the Infrared Astro-nomical Satellite mission indicates avery close correlation. Since the100-micron emission is not expectedto arise from PAHs, but instead frommuch larger grains of solid material,this tight spatial correlation mustmean that these two different kindsof interstellar materials are mixed ina constant ratio throughout thedifferent interstellar regions inthe galaxy.

Point of Contact: T. Roellig(650) [email protected]

Infrared Observations ofG0.18-0.04Janet P. Simpson, Sean W. J. Colgan,Angela S. Cotera, Edwin F. Erickson,Michael R. Haas, Mark Morris,Robert H. Rubin

Radio images of the center ofour Galaxy show a number offeatures that are unique in theGalaxy and that are very difficult toexplain. Some of these are demon-strated in the figure, which is a20-cm Very Large Array radio imageby F. Yusef-Zadeh and M. Morris,overlaid with contours showing thelocations of the Galactic Centermolecular clouds. A quarter of adegree from the Galactic Center

there is a long thin “Arc,” also calledthe Straight Filaments, that crossesthe Galactic Plane at right angles.The length and thinness of thesynchrotron radiation emitting Arc(and other arcs not in the figure),suggest that the Galactic Centerregion has a strong magnetic field;however, the excitation and sourceof the relativistic electrons emittingthe synchrotron radiation is notknown.

The Galactic Center H II region,G0.18-0.04, also called the “Sickle,”is located where the Arc crosses theGalactic plane. The Sickle appearsto be the ionized edge of the densemolecular cloud whose contours areshown in the figure. In the past, thesource of ionization of the Sickle has

42m30s 42m0s17h43m0s45m30s

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Fig. 1. The 20-cm Very Large Array radio image, overlaid with contoursshowing the locations of the Galactic Center molecular clouds. Sgr A is theGalactic Center. G0.18-0.04 (the Sickle) and the Pistol are labeled.


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been ascribed to both the interactionof the cloud with the magnetic fieldof the Arc and to the hot stars in theadjacent star cluster, AFGL 2004,also known as the “QuintupletCluster.” There is a smaller region ofthermal gas known as the “Pistol”;the star cluster AFGL 2004 liesbetween the Sickle and the Pistol.Because of the great obscurationtoward the Galactic Center, it is notpossible to see these regions atwavelengths visible to the eye;instead, one must use infrared andradio telescopes to view the region.The objective of this study is toascertain the relative locations of thestars, the ionized and molecular gas,and the sources of gas excitation anddust heating.

Far-infrared lines of C+, N+,N++, O0, O++, Si++, and S++ weremeasured with the CryogenicGrating Spectrometer on the KuiperAirborne Observatory. For the H IIregion, electron densities for boththe O++ and S++ zones wereestimated, and abundance ratioswere calculated for O++/S++, N++/O++, N+/N++, N+/O++, Si+/S++,and S++/H+. For the less excited gasin the interface region between theH II region and the molecular cloud,the incident photon flux and densi-ties were estimated from the C+and O0 lines and the far-infraredcontinuum.

Near-infrared images of theregion were taken by A. Cotera aspart of her Stanford University Ph.D.thesis (1995), supported by a NASAGraduate Student Research Fellow-ship at Ames. From the 1.65 and2.1␣ micrometer photometry of starsin the field and from the HydrogenBr gamma images, the extinction tothe region could be estimated. The

extinction is fairly uniform over theregion and is consistent with alocation in the Galactic Center.There is no indication of the densemolecular cloud that had previouslybeen suggested by other researchersto lie between Earth and the regionin the images of the star field. Theprevious suggestion of excitation ofthe Sickle by interaction of themolecular cloud with the magneticfield required that the cloud, whichrecedes at 25 kilometers per secondaway from Earth, produce theobserved 20- to 120-kilometers-per-second ionized gas in the H II regionby running into the magnetic fluxtubes of the Arc. Thus, both the Arcand the ionized gas would be on thefar side of the cloud from Earth inthis scenario. Since the near-infraredmeasurements of the stars and theionized gas demonstrate that the gasmust be on the near side of thecloud, this early suggestion cannotbe correct.

The observed lines were com-pared with predictions of models ofslab H II regions ionized by a clusterof luminous stars. This comparisonindicates that the source of ioniza-tion of the Sickle is probably the hotstars of the AFGL 2004 cluster, butthe Pistol has a lower ionization thanits proximity to the cluster wouldsuggest. More likely, the Pistol isionized by the extremely luminousstar that the Ames researchers foundto be located near the center of itsarc. Since the positions at somedistance from AFGL 2004 havehigher ionization than is predictedby the models, it is likely that thereare additional hot stars scatteredthroughout the region. The lowexcitation lines and far-infraredcontinuum from the molecular cloud

and interface region between thecloud and H II region are alsoconsistent with heating and excita-tion by the same stars. The electronsin the Arc probably originate in theionized gas of the H II region andare excited to relativistic energiesby magnetic reconnection of themagnetic field lines of the Arc andthe molecular cloud.

Point of Contact: J. Simpson(650) [email protected]

New 3.405-MicronInterstellar Emission fromOrganic HydrocarbonsGregory C. Sloan, Jesse D. Bregman

Polycyclic aromatic hydrocar-bons (PAHs) are a form of organichydrocarbon identified by theircomplex spectral emission in a richvariety of astronomical sources. Thisspectrum includes several emissionfeatures between 3 and 13 microns,originally described as the unidenti-fied infrared emission features. LouisAllamandola and his Ames collabo-rators identified the carriers of thisspectrum by their laboratory analysisof PAHs. These molecules typicallyconsist of 20-50 carbon atomsarranged in a flat matrix of aromaticrings, with hydrogen atoms bondedto the carbon on the edge. TheC-H bonds produce most of thespectral features observed fromthe ground; stretching modesproduce features at 3.3 microns andnearby; bending modes producefeatures at 8.6 microns and in the


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11.2–12.7-micron region. Theseorganic molecules may representmore than 15% of all interstellarcarbon, so a better understanding oftheir composition would give usinsight into the evolution of interstel-lar carbon material. Because PAHspectra are seen in so many sources,a better understanding of the emis-sion mechanisms would make themvery powerful probes of the interstel-lar medium.

PAH spectra are observedtypically at the edge of ionizedregions. One such region, the OrionBar, is a transition region betweenthe Orion Nebula, ionized by theultraviolet energy from the Trape-zium, and the molecular cloud tothe southeast. These transitionregions have strong gradients inultraviolet flux decreasing from theionized zone to the molecularregion. The Bar presents the observeron Earth with an edge-on geometrywhich makes it an excellent labora-tory to study how PAH emissionvaries with excitation conditions.

The 3-micron PAH emission inthe Orion Bar was observed using along-slit spectrometer at the UnitedKingdom Infrared Telescope inOctober 1995. These spectra allowone to trace the strength of the3.29-micron PAH feature, whichdominates the spectrum and arisesfrom a ground-state aromatic C-Hstretch; the weaker features observedat 3.40 and 3.51 microns; and theunderlying emission plateau whichstretches from 3.3 to 3.6 microns.These features peak on the ioniza-tion front, and drop in strength intoboth the ionized and molecularregions. The features decrease intothe ionized region because the harsh

ultraviolet field is destroying thePAHs there. They decrease into themolecular region because theultraviolet flux which excites thespectral features is being attenuatedby the high optical depths of theneutral and molecular gas in the Bar.In general, these features decreaseinto the molecular region exponen-tially, with a 1/e scale height ofapproximately 10 arcseconds.However, the PAH plateau, and the3.40- and 3.51-micron features showa layer of enhanced emissionroughly 10 arcseconds behind theionization front, right where emis-sion from H2 also peaks. Thisenhancement is especially notice-able in the 3.40-micron emissionfeature.

A careful analysis of both theshape and the strength of the3.40-micron feature reveals that itactually consists of two spectrallyand spatially distinct components.The main component peaks at3.395 microns and behaves spatiallyvery similarly to the PAH plateauand the 3.51-micron feature. Thesecondary component peaks at3.405 microns, and its emission isconcentrated 10 arcseconds behindthe ionization front, again, rightwhere the H2 emission peaks.

The spectral properties can beinterpreted in terms of recentlaboratory analyses of PAHs atNASA Ames by Bernstein, Sandford,and Allamandola and by Joblin,Tielens, Allamandola, and Geballe.Joblin et al. analyzed PAHs withattached methyl sidegroups, whichcontain aliphatic C-H bonds andproduce an emission feature closeto the position of the secondarycomponent, 3.405 microns.

Bernstein et al. analyzed what theydescribe as H-PAHs, or PAHs withadditional H atoms attached to thecarbon on the periphery of thePAHs. These atoms convert aromaticC-H bonds to aliphatic C-H bonds,producing an emission feature at3.395 microns, as well as the PAHplateau and emission feature at3.51 microns. In fact, their labora-tory spectrum of hexahydropyreneprovides the closest match yetattained to the astronomical PAHspectrum.

The evidence is growing that the3.40-micron feature arises from analiphatic C-H bond. Both of thecomponents at 3.40 microns thatwe have identified arise from such abond, although the bond resides indifferent carriers. Based on thedifferences in spatial behaviorbetween these components, itappears that the methyl sidegroupsare easily destroyed beyond themolecular hydrogen emission layer,whereas the H-PAHs survive right upto the ionization front.

Point of Contact: J. Bregman(650) [email protected]


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Progress in Space Technologies

Assessment of the CassiniCommand and DataSubsystemEdward A. Addy

Formal methods have beenpromoted as an effective means ofdeveloping software that requires ahigh degree of assurance. Yet todate, formal methods have notsignificantly affected softwaredevelopment practices. The difficultyof maintaining the fidelity of theformal model with the system as thesystem undergoes changes inrequirements and specificationsduring development has contributedto its failure to influence the devel-opmental practices. The goal of thisproject is to determine if the use of

theorem-proving within a formalmodel can be used to generate testcases for testing the actual systembeing modeled. The union of formalmodels with test-case generation willhelp to alleviate the difficulty ofmaintaining fidelity, and will provideuseful information in the form of testcases to the development team.

The functioning of the schedulerand interrupt handler throughanalysis of the Cassini Commandand Data Subsystem (CDS) sourcecode has been used as a case study.A formal model of this part of theCDS software was created, using theformal specification language,Prototype Verification System (PVS),which is based on a classic, typedhigher-order logic. The PVS systemincludes support tools and a theoremprover. This follows on from previ-ous research in which formal modelchecking was used to generate testcases for the actual system. The testdata and the model checking havebeen used jointly to maintain thefidelity of the model with the actualsystem as it is being developed. Thisproject has used theorem-provingwithin the formal model in a similarfashion, to generate test cases for theCDS and to increase the fidelity ofthe model to the CDS, as illustratedin the figure.

The source code from theCassini CDS related to the schedulerand interrupt handler functions wasanalyzed. The formal modelingprocess identified that the millisec-ond interrupt was not functioningproperly. The development teammodified the scheduler, improvingits performance and eliminating thepotential for improper memory

allocation. A preliminary PVS modelof the scheduler and interrupthandler functions has also beendeveloped.

Point of Contact: E. Addy(304) [email protected]

Automatic TelescopeProjectJohn Bresina

The primary objective of theAutomatic Telescope Project is toprovide advanced scheduling andautomation infrastructure so that thebenefits and performance of single-user automatic telescopes can bemade available to a large commu-nity of users, with no additionalpeople in the loop. In addition,Web-based assistance is providedfor “service observing,” which isbecoming the dominant operationsmode for large-scale, sophisticatedtelescopes. The benefits are adramatic reduction in telescopeoperating costs and an increase inboth scientific productivity and ease-of-use. The Associate PrincipalAstronomer (APA) enables electronicrequest submission, automaticloading and scheduling, and elec-tronic data return, all under thecontrol of a single astronomer (seethe figure for an illustration of thearchitecture). The advanced loadingand scheduling techniques providefair allocation of telescope time andsupport high-quality data collection.

The APA software tools havebeen extensively tested by G. Henryat Tennessee State University (TSU)

PROGRESS IN SPACE TECHNOLOGIES

P R O G R E S S I N S P A C E T E C H N O L O G I E S

Formal model

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Fig. 1. Use of theorum-proving ingenerating test cases to maintainformal model fidelity during systemdevelopment.

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and by the Fairborn Observatorystaff. The scheduler has beenexecuting nightly since January 1996for Fairborn telescope T8. The loaderhas been undergoing nightly testingfor the same telescope since April1996, and the Service ObservingAssociate (SOA) is undergoing

testing on the UK Infrared Telescope(UKIRT). There was enthusiasticreception of the APA from UKIRT,the Hands-On-Universe project, theFour College Telescope, and UK’sNew Generation AstronomicalTelescopes Project. John Daviescarried out a successful “live test”

of the SOA at UKIRT and demon-strated the system to senior staff ofthe multinational Gemini project(and others).

Point of Contact: J. Bresina(650) [email protected]


PA

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Fig. 1. Associate Principal Astronomer architecture.

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Guide Star Tracker forGravity Probe B RelativityMissionJohn H. Goebel

The guide star tracker for theGravity Probe B (GPB) RelativityMission is used to define the inertialreference frame against which therelativistic effects of a satellite in apolar Earth orbit can be measured.The tracking telescope is cooled tosuperfluid helium temperature

(1.87␣ kelvin) in order to accommo-date the gyroscope readout detectorsof the Superconducting QuantumInterference Device (SQUID).Because both the gyroscope andguide telescope are rigidly mountedtogether in the liquid-helium-cooledportion of the satellite, the starlightsensing detectors and preamplifierelectronics must function withoutdisturbing either the gyroscopes orthe telescope wavefront. Trackingaccuracy of the order of 10␣ milliarc-seconds is required, implying that

thermal disturbances must be kept toa minimum.

The Space Technology Branchhas contributed to the star sensordevelopment effort for GPB byassisting in the design, construction,development and testing of thephotodiode and cooled electronics.This effort is a collaboration withscientists and engineers at StanfordUniversity, Marshall Space FlightCenter, Goddard Space FlightCenter, Ames Research Center,Lockheed-Martin Corporation, andvarious suppliers of componentparts.

A photograph of the Revision Bhybrid electronics circuit for the starsensor that is mounted in thecryogenic vacuum vessel is shownin the figure. The sensor has beendemonstrated to meet the require-ments for functioning in the cryo-genic environment by operating at asomewhat elevated temperature of70 kelvin with a power dissipationnot exceeding 2 milliwatts. Opera-tion of the sensor at temperaturesdown to 30␣ kelvin has been demon-strated at power dissipation less than1␣ milliwatt.

Point of Contact: J. Goebel(650) [email protected]

Pulse-Tube CryocoolerDevelopmentPeter Kittel

Pulse-tube coolers have uniqueadvantages over the other coolersthat are usually considered for NASAspace missions. Because they have


Fig. 1. Revision B Hybrid Circuit. This circuit is 0.400 inches in diameterand includes two circular silicon photodiodes and four square silicon fieldeffect transistors. Light from the guide star is focused on the detectors whichconvert the light to electrical current which in turn is amplified by thetransistors. The circuit is thermally isolated from the cryogenic environmentso that it can operate at an elevated temperature of 70 kelvin.

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no moving parts in the cold part ofthe cooler, they have inherently verylong lifetimes and very low levels ofvibration. However, they are arelatively new technology andrequire further development toachieve the thermal efficiency ofmore mature coolers such as Stirlingcoolers. The first figure shows themain components of a pulse-tubecryocooler.

The compressor (at roomtemperature) provides an oscillatinggas pressure which moves gas intoand out of the cooler. The regenera-tor consists of a tightly packed bedof fine screens that absorb anytemperature oscillations in the gas.The compressor end of the regenera-tor is at room temperature and theother end is cold. The pulse tubeisolates the cold junction from theorifice and reservoir at room tem-perature. A properly adjusted orificecreates a special relationshipbetween the pressure oscillations inthe pulse tube and the gas flow suchthat heat is drawn from the coldjunction and deposited at the orifice.

In FY96 great progress wasmade in understanding and improv-ing the operation of two of the maincomponents of the cooler—theregenerator and the orifice.

For the screen mesh in theregenerator to adequately absorbtemperature oscillations in the gaspassing through it, it must have alarge surface area and a large mass.These requirements suggest a largenumber of very fine screens and ahigh impedance to the gas flow. Theregenerator must not be too restric-tive, because this would reduce thepressure and flow available forcooling at the pulse tube. It is crucialto find the best compromise between

absorbing temperature oscillationsand allowing adequate flow.

The behavior of this region ofthe cooler has been difficult topredict; measurements of pressuredrop with oscillating flow havedisagreed with predictions basedon steady-flow data. Therefore,measurements were made to charac-terize the screen mesh of the regen-erator under oscillating flow

conditions that were similar to thosethat would exist in actual use. Thesemeasurements showed that thepressure drop at frequencies near60␣ cycles per second was 20–30%less than that predicted from steady-flow data. These improved data(shown in the second figure) willallow much better optimization ofthe regenerator screens.


CompressorRegenerator

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Fig. 1. Components of a pulse tube-cryocooler.

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Various amplitudes60 Hz data

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Fig. 2. Pressure drop in a 325-mesh regenerator. Solid curve is steady-flowdata. The data points are the instantaneous pressure drop during 60-cycleruns for a variety of amplitudes.

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The orifice serves to adjust therelationship between oscillating gaspressure and gas flow in the pulse-tube section. An analysis of thesystem shows that much morecooling power could be obtained ifsufficient adjustment of this relation-ship could be achieved. However,the range of adjustment availablefrom a simple orifice is not enoughto allow the utilization of the extracooling power that the system iscapable of. What is needed is adevice that has “inertance” inaddition to the dissipation of theorifice. To use an electrical analogy,the “resistance” represented by theorifice needs to be replaced by adevice with “inductance.” A devicewith the inertance needed turns outto be a long narrow tube; typically itwould be 2-3 millimeters in diam-eter and several meters long.

Preliminary testing has beenperformed with such an inertancetube in place of the orifice, and thecooler performed considerably betterthan it did with the orifice; thisshows that the analysis is on theright track. More improvement isexpected as understanding of theoperation of the inertance tube isgained and its parameters areoptimized.

Point of Contact: P. Kittel(650) [email protected]

Automated Space SystemExperimental TestbedProjectChristopher Kitts

The Automated Space SystemExperimental Testbed (ASSET)project is an Internet-based, justified-operations control system for smallsatellites. The project’s objectivewas to establish a global spacecraftcontrol network in order to (1)␣ pro-vide operational support for a varietyof low-cost missions, and (2) providea high-risk, low-inertia testbed forvalidating spacecraft autonomystrategies.

The operational system providesan automated link between a varietyof users (including principal investi-gators, students, operators, and thepublic) and a multitude of spacecraftpayloads. The ASSET system iscapable of accepting goal-levelexperimental parameters andplanning and scheduling system andspacecraft activities, and of conduct-ing mission and health-relatedtracking, telemetry, commandingoperations with the spacecraft, anddelivering the experimental data tothe original experimenter. To do this,the ASSET system componentsinclude a central mission controlcenter, geographically distributedground stations, a variety of space-craft, Internet and HAM radiocommunications links, and numer-ous payload components.

ASSET provided an unparalleledopportunity for rapid experimenta-tion with revolutionary autonomytechnologies in a real-world, com-plex space system. The initial ASSETimplementation is supporting the

New Millennium ProgramAutonomy Technical IntegrationExperiments concerning datadistribution, principal investigatorinterfacing, beacon operations,ground system automation, and faultmanagement.

Point of Contact: C. Kitts(650) [email protected]

Amphion andMeta-AmphionMichael Lowry

Most of today’s programmingproblems involve a programmerbuilding special domain-orientedsoftware libraries (modules thatperform a specific function) for everydomain. Then users must makesoftware program calls to thesemodules in order to get the workdone. The correctness of theseprograms is difficult to prove.Amphion automates the use of thesesoftware libraries. It enables a userto state a problem in an abstract,graphical visual programmingnotation, rather than requiring theuser to construct a solution bymanually composing softwarecomponents. Amphion then auto-matically generates a programconsisting of calls to the librarycomponents to solve a specificproblem. Moreover, as part of thisgeneration process, which is donethrough automatic theorem-proving,Amphion produces a mathematicalproof that the program is correct.Formal mathematical methods are


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applied for program verification. Ifperformed manually, this formalproof is costly and only becomescost-effective for safety-criticalsystems.

Meta-Amphion is a system thatwill enable software-library develop-ers to create and maintain their ownspecialized Amphion systems. Inessence, Meta-Amphion is the next-generation application-generatortechnology. Using Amphion, it takeson average an order of magnitudeless time for a user to develop adomain-oriented problem specifica-tion than to manually generate anddebug a program. Equally important,a user does not need to learn the

details of the components in asoftware library. This removes asignificant barrier to the use ofNASA’s software libraries. The figureshows a snapshot of a science-opportunity visualizer for the CassiniMission. The code for the visualizerwas generated automatically byAmphion.

The benefit of Meta-Amphion isto enable the widespread develop-ment of specialized Amphionsystems, thus realizing the dualbenefits of automated formal meth-ods and domain-specific automaticprogramming. Meta-Amphion is theset of tools and infrastructure neededto elevate programming from the

code level to the declarative,specification level. The genericAmphion system is nearly mature,having gone through an extensivealpha/beta version that has alreadybeen tested by customers.

Point of Contact: M. Lowry(650) [email protected]

Focal-Plane Sensor ArrayDevelopment forAstronomy in SpaceMark E. McKelvey,Robert E. McMurray, Jr.,Craig R. McCreight

A team at Ames Research Centeris evaluating the suitability of anumber of detector and readout-device technologies for space-infrared astronomy applications. Thisprogram aims to foster developmentof focal plane array (FPA) detectortechnology that will allow reliablebackground-limited infrared (IR)astronomy from space-based plat-forms such as the Space InfraredTelescope Facility (SIRTF). Advancesin microelectronics to provideoperation of low-noise, low-powerdevices in the radiation environmentfound in Earth orbit are keys to thesuccess of this program.

Evaluations of state-of-the-artImpurity Band Conduction (IBC)focal plane detector arrays producedby several manufacturers are con-tinuing for applications in the5–30-micron wavelength range.These detectors rely on a thin, highlydoped IR-active layer to provide


Fig. 1. Amphion-generated science-opportunity visualizer for theCassini Mission.

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high quantum efficiency from asmall detector volume, minimizingthe ionization cross section forcosmic ray events. A high-purityblocking layer prevents excessivedark current, despite the high dopinglevels in the IR-active layer. IBCarrays also exhibit wider spectralresponse than alternative photo-conductor (PC) architectures,without many of the performanceanomalies associated with PCdevices. IBC architectures are wellsuited to modern epitaxial fabrica-tion methods, and the technologyhas progressed to the point wherelarge-format hybrid FPAs that are

sensitive to IR wavelengths as longas 28 microns can be reliablyproduced.

Work in FY96 was concentratedon evaluating the performance oflarge-format (to 256 × 256 detectorelements; see figure) state-of-the-artIBC detector arrays in simulatedon-orbit radiation environments,using the 76-inch Crocker Cyclotronon the campus of the University ofCalifornia at Davis to provide a high-energy proton beam for devicetesting. These tests, in collaborationwith astronomers from CornellUniversity and from the University ofArizona, have shown a marked


difference in radiation-damagesusceptibility between similar arraysfrom different manufacturers. Thisdamage is manifested as dose-dependent activation of dark currentthat could be of crucial importanceto the Wide-Field Infrared Explorer(WIRE) or SIRTF science missions.The results of the Ames tests arebeing fed directly back into themanufacturing process in order tohelp advance the state of the art.

Improved IBC devices from ajoint Ames/Santa Barbara ResearchCenter development are presentlybeing evaluated. These 256 × 256arrays utilize a simplified unit cellarchitecture and new samplingtechniques to achieve read noiselevels as low as 12 equivalentelectrons. These devices are proto-types for the flight detectors to beused on the SIRTF Infrared ArrayCamera (IRAC). The Ames group willcontinue to play an important role inthe definition and execution of theIRAC detector acceptance andqualification test program.

Other recent efforts involvehardware and software upgrades tothe suite of test instrumentationmaintained in the detector labora-tory. Recent upgrades have allowedeasier manipulation of the data filescollected from these large-formatdetector arrays. A project is presentlyunder way to enhance the capabilityof the data acquisition system tohandle arrays as large as 1024 ×1024 elements. Continuous softwaredevelopment has provided improvedtest flexibility, automation, andrepeatability. Work on maturing IBCtechnology and improved readouts,along with other sensor technologies

Fig. 1. 256 × 256 element infrared detector array.

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in ongoing efforts, will enhanceoverall IR focal-plane performancein NASA space- and ground-basedapplications.

Point of Contact: M. McKelvey(650) [email protected]

Intelligent Execution forAutonomous SpacecraftBarney Pell

An executive system is an event-driven and goal-oriented agentthat␣ coordinates run-time activityamong a set of components involvedin a control system. As such, itprovides a language and a frame-work in which software designerscan express how planning, control,diagnosis, and reconfigurationcapabilities are to be integrated intoan autonomous system. It canrequest and execute plans involvingconcurrent activities among sub-systems, in the presence of uncer-tainty in the success, timing, oroutcomes of activities. A smartexecutive provides a language forexpressing goal-decompositions andresource interactions. When inter-preting this language at run-time, theexecutive automates the decomposi-tion of goals into smaller activitieswhich can be executed concur-rently, thus automating aspects ofthe labor-intensive sequencingfunction in spacecraft operations.

This task investigates thedevelopment of increasingly intelli-gent execution systems, their role inautonomous control systems, andtheir practical application as anenabling technology for autonomous

space missions. We are currentlygrounding the research by develop-ing the smart executive, part of theRemote Agent (RA) being developedfor the Deep Space One (DS1)mission, part of NASA’s NewMillennium Program (NMP). DS1will autonomously navigate toasteroids and comets and will beable to achieve its mission in theface of a wide variety of faults,including total loss of control fromEarth.

As an integrating technology, anexecutive enables each softwarecomponent to be expressed indepen-dently, but it controls the interac-tions among those components sothat the overall activity of the systemachieves global constraints asdictated by a high-level plan. Thisdramatic increase in modularsoftware design reduces develop-ment and integration costs andincreases software reuse both withinand across missions. The goal-directed task-decomposition auto-mates much of the labor-intensivesequencing process in spacecraftoperations. This capability alsoenables a new generation of adap-tive controllers, in which differentcontrol modes are developed thatare switched by a smart executivebased on feedback from theenvironment.

The DS1 mission will validatethe smart executive and the entireRA in the context of actual spaceflight. The architecture will serve asthe baseline for the next generationof space missions, and will bedeployed to a wide variety ofmanned and unmanned spacecraft;it will also increase the level ofautonomy in other control systems,such as aircraft and factories.

FY96 accomplishments includecompletion of the rapid prototypingeffort in November 1995, demon-stration of the prototype, andpresentation of the smart executiveto the NMP in the December 1995Technology Readiness Review,which accepted the RA architectureto be developed for the DS1 mission.

Point of Contact: B. Pell(650) [email protected]

New Millennium ProgramDeep Space 1 FlightSoftware ProgramManagementScott Sawyer

The New Millennium Program’sDeep Space One (NMP DS1) FlightSoftware team comprises staff fromAmes and the Jet Propulsion Labora-tory (JPL) (which also includesindividuals from the Air ForcePhillips Laboratory, TRW, Carnegie-Mellon University, and Thinkbank,Inc.). The team is developing flightsoftware (FSW) for the first missionof the New Millennium Program(NMP). The Ames team (along withpart of the JPL team) is dedicated todeveloping and testing the “RemoteAgent” architecture of the FSW. Theremote agent (RA) integrates rule-and model-based fault detection,isolation, and recovery; advancedplanning and sequence managementcapabilities; and a system executivethat serves as an autonomous agentcontrolling and coordinating thesatellite’s behaviors during normal


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and abnormal operations. The RA iscapable of responding autonomouslyto system and payload faults andmalfunctions, establishing contactwith ground operations personnelwhen necessary, and replanningportions of the mission onboard toaccommodate unanticipatedchanges in spacecraft performanceor objectives. The DS1 mission willbe the first ever to fly an onboardautonomous agent flight system.

Program management objectivesare (1) managing Ames and JPL teampersonnel; (2) defining developmentschedules, descope options, andcontingency plans when necessary;(3) preparing and presenting statusreviews and briefings to programmanagement, Center management,and review boards; (4) makingbudget and workforce projections;and (5) acquiring the necessaryresources to allow the team toaccomplish its goals. Technicalobjectives include flight/groundinterface design, RA design over-sight, and the performance ofengineering duties related toautonomous systems such asdefining command and telemetrysystem requirements, fault protectionsystem policies, and FSW validationpolicies.

Successful development of anRA FSW architecture for NMPDS1 will identify new avenuesof research which will guide thegrowth and development of the nextgeneration of “thinking” spacecraft.The RA architecture will beexpanded to be used in a widevariety of manned and unmannedvehicles. By carefully selectingapplications projects to accompany

the research, Ames can effectivelyfocus the research efforts on practi-cal problems at the cutting edge oftechnology.

Point of Contact: K. Swanson(650) [email protected]


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Human Exploration and Development of Space Enterprise

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O v e r v i e wNASA’s Human Exploration and

Development of Space (HEDS)enterprise brings the frontier of spacefully within the sphere of humanactivity. Ames supports the HEDSenterprise by conducting research,managing spaceflight projects, anddeveloping advanced technologies.An objective of these efforts is toseek knowledge of physicochemicaland biological phenomena that canbe fully explored only at very lowgravity levels. This objectiveembraces the quest for knowledgeof the role and influence of gravity inliving systems—one of the elementsof NASA’s astrobiology activities.A second objective is to developtechnologies for advancing humanexploration of space and achievingroutine space travel. A complemen-tary objective is to apply knowledgegenerated in pursuit of these objec-tives, where feasible, to enrich lifeon Earth. During FY96, numerousresearch and technology efforts thataddressed the following goals ofthe HEDS enterprise wereaccomplished:

• Increase knowledge of nature’sprocesses using the spaceenvironment.

• Advance human exploration ofthe solar system.

• Achieve routine space travel.• Enrich life on Earth through

educational, commercial, andtechnological opportunities inspace.

New knowledge and an increasein the understanding of nature’sprocesses related to the influenceof gravity on living systems are

acquired by a two-prongedapproach: (1) Research is conductedon the ground and in space over arange of gravitational levels and witha variety of biological specimens;and (2) specialized equipment andadvanced technologies are devel-oped to support life-sciencesresearch on the ground and in space.The knowledge thus acquired is thenintegrated and disseminated by usinginformation technology.

In this report, new life-sciencesresearch findings are presented; forexample, new biochemical assays ofbone collagen degradation, whichare useful tools for monitoring bonemineral loss (a major biomedicalproblem of long-duration humanspaceflight). Other research showsthat both cerebral blood flowvelocity and cerebral oxygenationdecrease prior to fainting. Thisfinding improves our understandingof the typical orthostatic intoleranceand fainting observed in manyastronauts following spaceflight.Additional work has focused onunderstanding the process of dualadaptation (or separate adaptationsto two mutually conflicting sensoryinputs) as it applies to the alteredgravity environment. These studiesshould provide greater insight intothe processing of altered gravita-tional inputs directly relevant to anastronaut’s ability to function wellin space.

Technological advancesdescribed in this report have numer-ous applications in the medical andbiomedical fields. The VirtualEnvironment Surgery Workbench, incombination with software originallydeveloped for an Ames spaceflightexperiment with rodents, has

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attracted much interest from recon-structive surgeons, and this tool isexpected to decrease the trainingtime of a skilled craniofacialreconstructive surgeon from 20 to10␣ years. In addition, this technologymay soon offer doctors in theemergency room real-time, high-fidelity, three-dimensional informa-tion so that accurate diagnoses andpotential reconstructive alternativescan be quickly determined.

Neural net software develop-ment has resulted in another medicaltechnology aimed at increasing thecapability of neurosurgeons. Thesoftware enables a robotic probe to“learn” a patient’s brain characteris-tics, making it easier for a surgeon tolocate the exact position of a tumorafter surgery is under way and thenormal swelling of brain tissuecomplicates the process.

In the ongoing effort to developmethods to monitor vital bloodconstituents, a prototype system thathas application to astronaut health,space life sciences, and Earth-basedmedicine has been created. Concen-trations of ions in flowing bloodplasma can now be measuredby a computer-controlled data-acquisition system known as theBlood Flow Ion Analyzer. Liver-function support systems are directbeneficiaries of this technology, asthere is a specific need to continu-ously monitor and control ionconcentrations of processed bloodplasma.

A spinal compression harnessdesigned as a potential aid toastronauts in combating back painduring spaceflight is also of interestto orthopedic therapists. The harnessallows doctors to perform magneticresonance imaging while positioning

the patient in the characteristicsupine position but with loads addedto the spinal column simulatingthose that occur naturally in theupright posture. Such imagingcapability will provide a greaterrange of diagnostic data for doctorswho treat the millions of people whosuffer back pain.

Another recent Ames projectinvolving telemedicine, Spacebridgeto Russia, linked three U.S. hospitalsand a university with two medicalcenters in Moscow via the Internet.Ames is responsible for developingthe technical architecture as well asproviding direction in setting up theInternet connections and the motionvideo consultation and videoteleconferencing features. Thesecapabilities have already enabledtelemedicine consultations amongall test users, and plans are underway to utilize the system as aneducational tool for hospitals.

As part of the HEDS goal toexplore the solar system, Ames hasactively pursued life-support meth-odologies relating to atmosphereregeneration, water purification,recycling from waste materials, andfood production. The work has givenbirth to new concepts of reducingspacecraft power and weightrequirements.

Research in the unique environ-ment of space requires specializedequipment to operate withinmicrogravity and assure that theresearch conducted does not pose ahealth or safety risk to the humancrews. One such piece of equipmentdeveloped during the past year is thestandard interface glovebox, whichis now flying aboard the Mir station.This device was designed to providean enclosed workspace that contains

particulates, odors, and the kinds ofchemicals and biological specimensrequired by life scientists.

To help astronauts achievemaximum productivity during theparticularly crucial first days offlight, researchers at Ames havebeen working on ways to reducethe space adaptation syndrome.Autogenic-Feedback Training (AFT)seems to be effective in controllingmotion sickness under a variety ofconditions, including spaceflight.The AFT exercise technique can alsobe used to control blood pressureand thus ameliorate postflightorthostatic intolerance.

Lower-body negative pressureequipment specifically developed asa potential countermeasure for thedebilitating effects of long-termhuman spaceflight has been modi-fied to provide a variety of loadinglevels on the lower body. In combi-nation with a treadmill, the equip-ment has applications both as acountermeasure to the atrophy ofthe musculoskeletal system duringspaceflight and as a rehabilitativetool for treating patients sufferingspinal trauma on the Earth.

The use of a device that com-bines resistive exercise with aerobictraining is described. Presently,cardiovascular exercise is empha-sized during Space Shuttle missions;however, research with the “SX-1Variable Resistance Exercise Device”suggests that astronauts may be ableto maintain muscle size and strengthwhile also maintaining bone densityduring spaceflight.

It is vitally important that theresults of HEDS research be quicklydisseminated to the public, that is,the commercial sector and the

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educational and scientific communi-ties. To this end, life-sciencesspaceflight data are being publishedin the scientific and popular litera-ture and archived in the NationalSpace Science Data Center at theGoddard Space Center. Ames is alsoactively engaging teachers andstudents to promote science educa-tion of our nation’s youth.



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Biochemical Markers ofBone Metabolism in a RatSpaceflight ModelMeena Navidi, Jeanne Wren,Sara Arnaud

Newer biochemical assays ofbone collagen degradation productsin urine are useful tools for monitor-ing bone loss (a major concern ofspaceflight) and the effects ofcountermeasures to prevent boneloss in human adults. The resultsreflect the collective metabolicactivities of bone resorption in theentire skeleton, a process that isactivated by exposure to a head-down tilt, bed-rest spaceflightmodel. These techniques have yet tobe applied to small-animal modelsof weightlessness. Through histo-logic methods, the decrease in newbone formation in the rat tibia duringspaceflight is well documented.Recently, increases in osteoclastnumber and resorption wereobserved in highly localized areasin the proximal tibia. Ground-basedmodels of juveniles of the samespecies show morphologic changesconsistent with reduced boneformation in unloaded hind limbswith no evidence for increasedresorption. The mature rat, exposedto the same ground-based modelwith unloaded hind limbs for28␣ days, reveals less bone mineralcontent in the femur, compared withambulatory controls. This apparentbone loss is thought to be causedby increased resorption as well as

depressed formation, but no histo-logic or biochemical measurementssupport this idea.

To evaluate bone resorption,an assay that measures deoxypyri-dinoline (Dpd), a product of thebreakdown of collagen crosslinks inbone was used. This assay is cur-rently regarded as one of the mostspecific and sensitive markers ofbone resorption. The 24-hourexcretion of Dpd in two-month-oldjuveniles was more than seven times

higher than in six-month-old matureanimals (see the figure). This agedifference reflects growth rates thataverage 2-3 grams per day injuveniles and are stable and essen-tially zero in mature animals.Exposure to the spaceflight modelfor 14 days reduced Dpd excretion,whereas it remained unchanged inthe control juveniles. In contrast,mature rats showed increases in Dpdexcretion after 14 days exposure tounloading, as shown in the figure.

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These results illustrate themarked, age-dependent differencesin the response of the skeleton to aweightless environment. Results inthe mature animals, who at sixmonths of age have acquired 96%of the bone they will have in theirlifetimes, are similar to the increasesobserved in human adults. There isan increase in bone resorption afterunloading the skeleton, a situationfavorable to bone loss unlessaccompanied by an increase in boneformation. Alkaline phosphatase, acirculating marker of bone forma-tion, was unchanged in this study.The opposite result, suppression ofhigh resorption rates in juveniles,could be related to depressed growthhormone or a growth factor duringexposure to the model. While it isclear that the adaptation of theskeleton to microgravity requiressite-specific changes in the rates offormation and resorption in weight-bearing bones (to modify bonestructure for new loads), there alsoappears to be a systemic responsereflected in bone marker assaysthat quantifies overall skeletalmetabolism.

Point of Contact: M. Navidi(650) [email protected]

CerebrovascularResponses Prior toFaintingKana Kuriyama, Toshiaki Ueno,Richard E. Ballard,Donald E. Watenpaugh,Suzanne M. Fortney,Alan R. Hargens

Reduced orthostatic tolerance,commonly observed after space-flight, occasionally causes faintingduring standing. Prefainting condi-tions are usually manifested bysymptoms such as a sudden drop ofheart rate or blood pressure that isfollowed by loss of consciousness ifstanding is continued. Although thecerebrovascular system may play animportant role in postflight fainting,there have been few reports con-cerning cerebral hemodynamicsprior to fainting. This study wastherefore undertaken to investigatecerebrovascular responses bymeasuring cerebral blood-flowvelocity and cerebral tissue oxygen-ation prior to fainting, using lower-body negative pressure (LBNP) as anorthostatic stress.

Seven healthy male volunteerswere exposed to supine LBNP insteps of 10 millimeters Mercuryevery 3 minutes until prefaintingsymptoms were detected. Bloodpressure and heart rate were mea-sured with an automatic finger-cuffdevice. Cerebral blood-flow velocity

within the middle cerebral arterywas measured with transcranialDoppler sonography. Cerebral tissueoxygenation was monitored usingnear-infrared spectroscopy over theforehead.

During the initial stages ofLBNP stress, when blood pressuredecreases and heart rate is elevated,these cardiac responses are causedby blood pooling in the legs. Butas LBNP continues, cardiac insuffi-ciency occurs prior to fainting. Thisstudy focused on the 2-minuteperiod prior to the fainting endpointwhen LBNP was stopped. In atypical subject, blood pressurecontinued to decrease gradually asfainting was approached (see thefigure). Heart rate decreased rapidlyin the final 30 seconds, signifyingcardiovascular insufficiency justprior to fainting.

The new finding of this studyis that both cerebral blood-flowvelocity and cerebral tissue oxygen-ation decrease prior to fainting. Thedecrease of cerebral blood-flowvelocity can be explained as adecrease of cerebral blood flow ora dilatation of the middle cerebralartery. The decrease of cerebraltissue oxygenation can be explainedas a decrease of cerebral blood flowor less likely, a decrease of cerebraltissue metabolism. Therefore, it isprobable that cerebral blood flowdecreases just prior to fainting.

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In conclusion, during LBNP-induced fainting, cardiac insuffi-ciency primarily occurs, resultingin the failure of cerebrovascularcirculation. This study improves theunderstanding of postflight faintingin astronauts and may aid in thedevelopment of preventive methods.

Point of Contact: A. Hargens(650) [email protected]

Chronic Exposure toHyper-G SuppressesOtolith-Spinal Reflex inthe RatNancy G. Daunton,Merylee Corcoran, Robert A. Fox,Li-Chun Wu

As part of an ongoing effort tounderstand the neural mechanismsunderlying adaptation to alteredgravity, behaviors reflecting thefunction of gravity receptors (otolithorgans) in the inner ear (for example,air-righting reflex, orientation) of therat have been studied followingchronic hyper-gravity (hyper-G)exposure and found to be consider-ably altered. In addition to thebehavioral data, morphologicalstudies conducted by Ross inconjunction with the behavioralstudies have shown that there is areduction in numbers of synapses onotolithic hair cells in the utricularmaculae of animals exposed to thesame chronic hyper-G conditions.These behavioral and morphologicalfindings suggest that the sensitivity orgain in the otolithic system may be

Fig. 1. Blood pressure, heart rate, cerebral blood-flow (CBF) velocity, andcerebral oxygenation with emphasis on the final 2 minutes prior to lower-body negative pressure (LBNP)-induced fainting. Baseline values of eachmeasurement (n) represent supine data obtained just before startingLBNP protocol.

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decreased following chronichyper-G exposure.

One way to evaluate the gain orsensitivity in the otolithic system isto use the “free-fall” response, whichis an otolith-spinal reflex elicited bya sudden brief vertical-linear accel-eration or drop. Using electromyo-graphic (EMG) techniques, thisresponse has been demonstrated in anumber of muscles in animals andhumans. The earliest component ofthis response is dependent on intactotolith organs and does not habitu-ate over trials.

The otolith-spinal reflexresponse to sudden free-fall wasused to monitor sensitivity or gainin the otolithic system followingchronic exposures to hyper-G. Theinvestigators hypothesized that theamplitude of the early EMG responsewould be lower in animals exposedto hyper-G than in animals experi-encing only the normal 1-Genvironment.

A free-fall apparatus wasdeveloped that allows the animal,in a prone position, to be droppedsuddenly over a 40-centimeterdistance and then gently stopped bypairs of “soft springs.” This deviceprovides a sudden, vertical-linear-accelerative, free-fall stimulus to theanimal being tested. Animals wereinstrumented with EMG electrodesin the gastrocnemius muscle of thehindlimb. The EMG response, alongwith acceleration of the animal, wasrecorded during 10 drops for eachanimal. The animals were testedwithin 3.5 to 9 hours followingchronic (7 to 14 days) exposures tohyper-G produced by centrifugationon the Ames Research Center24␣ Foot-Diameter Centrifuge.

Analysis of the data showed thatin animals exposed to hyper-G, themajority of responses (61%) to thefree-fall stimuli were of very lowamplitude (suggesting low sensitivityor gain), while normal, controlanimals had very few (13%) low-amplitude responses (see the figure).Furthermore, a significantly higherpercentage of responses were lowamplitude in animals exposed to2.8␣ G than in those exposed to2.0␣ G. This suggests greater loss ofsensitivity or gain with centrifugationat higher G levels. In all casesanimals exposed only to the rota-tional component of centrifugationhad response amplitudes similarto those seen in normal controlanimals that were not exposed tocentrifugation.

The results of this study suggestthat chronic exposure to increasedgravitational conditions leads to adecrease in the sensitivity or gain ofthe gravity-sensing (otolith organ)portion of the vestibular system.Furthermore, a greater degree ofsuppression is produced by expo-sures to higher G levels. Thisdecreased sensitivity may underliethe deficits in otolith-mediatedbehaviors seen following chronichyper-G exposure and may berelated to the reduced numbers ofsynapses found in otolith organsunder the same conditions. Thecritical next question is whether thefree-fall response will be increasedfollowing chronic exposure tomicrogravity. If that is the case,

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important evidence will be obtainedon how the otolith organ systemis modified to subserve optimalvestibulo-spinal function (orienta-tion, postural control, locomotion) inaltered gravitational environments.

Point of Contact: N. Daunton(650) [email protected]

“Dual Adaptation” toSpace-Related SensoryRearrangementsRobert B. Welch

A series of studies is examiningthe process of “dual adaptation” in avariety of atypical sensory environ-ments representative of those likelyto be experienced by astronauts. Theterm “dual adaptation” refers to theacquisition of separate, relativelyindependent adaptations to two (andperhaps more) mutually conflictingsensory environments resulting fromrepeated alternation betweenexposure and adaptation to one ofthe sensory environments andexposure and adaptation to the otherenvironment. Evidence of dualadaptation is seen in a progressivedecline in (1) the perceptual and/orbehavioral interference that occursat the initial transition between thetwo sensory conditions, (2) theamount of exposure necessary toproduce asymptotic adaptation,and/or (3) the amount of adaptationacquired after a given amount ofexposure. During FY96, threeinvestigations of dual adaptationwere completed.

The first investigation,conducted by R. B. Post (Universityof California, Davis) and R. B. Welch(NASA Ames Research Center),measured perceived movement ofa stationary visual stimulus duringhead movements, known as “appar-ent concomitant motion” (ACM).ACM was measured both beforeand after exposure periods in whichsubjects performed voluntary headoscillations while viewing a spot thatmoved in conjunction with the head.During these intervals, subjectslooked at the spot as it movedalternately in the same direction asthe head was moving during either0.25 or 2.0 hertz head oscillations,and then in the opposite directionas the head at the other frequency.After a period of exposure, the visualstimulus came to be perceived asstationary only if it was caused tomove in the same direction as thatviewed during adaptation at thesame frequency of head motion.Thus, these results confirmed thepresence of dual adaptation of ACMin which the stimuli used to identifythe prevailing sensory environmentwere those associated with head-movement frequency.

In the second investigation,conducted by R. B. Welch(NASA Ames Research Center),B. Bridgeman and J. A. Williams(University of California, SantaCruz), and R. Semmler (Universityof Clausthal, Germany), two experi-ments examined the possibility thatthe human vestibulo-ocular reflex(VOR) is subject to dual adaptation,as well as “adaptive generalization,”which is the ability to adapt morereadily to a novel sensory rearrange-ment as a result of prior dual-adaptation training. In Experiment

One, subjects actively turned thehead during alternating exposure to(a) the visual-vestibular rearrange-ment (target/head gain = 0.5), and(b) the normal situation (target/headgain = 0.0). These conditionsproduced both adaptation anddual adaptation of the VOR, but noevidence of adaptive generalizationwhen tested with a target/head gainof 1.0.

Experiment Two, in whichexposure to the 0.5 gain entailedexternally controlled (that is, passive)whole body rotation, resulted inVOR adaptation, but no dualadaptation. As in Experiment One,no evidence of adaptive generaliza-tion was found. It was concludedthat it was the absence of a salientdiscriminative cue in the passiverotation experiment that preventeddual adaptation from occurring.

In the third investigation,conducted by R. B. Welch andN. Daunton (NASA Ames ResearchCenter), R. Fox (San Jose StateUniversity), and M. Corcoran andL. Wu (NASA Ames ResearchCenter), albino rats underwent four,7-day periods of continuous 2-Gexposure, by means of centrifuga-tion, which alternated with four,7-day periods of normal gravity(1␣ G). Before and after each 7-dayperiod, subjects were measured on(a) their righting reflex whendropped suddenly from an initiallysupine position into a vat of water40 centimeters below (“air righting”),and (b) swimming behavior afterstriking the water. Latency to theoccurrence of air-righting was foundto be subject to a form of dualadaptation. Specifically, animalsthat were repeatedly tested showeda significant improvement in mean


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speed of air righting (+47%;p = 0.008), while control animalswho received 2-G exposure, butwere only tested on righting (andswimming) after the last of the 7-dayexposure periods, showed only amarginally significant (p = 0.12)25% improvement in meanair-righting speed.

Point of Contact: R. Welch(650) [email protected]

TECHNOLOGY APPLICATIONS TO HUMAN

HEALTH

Virtual EnvironmentSurgery WorkbenchMuriel D. Ross

The research and developmentof a virtual environment (VE) surgeryworkbench was undertaken by theBiocomputation Center in FY96. Thisworkbench will be used for trainingreconstructive surgeons and forpatient-specific planning of complexcraniofacial and other reconstructivesurgeries. The virtual environmenttechnology will be useful to theHuman Exploration and Develop-ment of Space (HEDS) Enterprise fortraining astronauts for long-termmissions in space. It will provide VEsimulation capability during space-flight to help astronauts respondappropriately to unanticipatedemergencies.

The Immersive WorkBench(Fakespace, Mountain View, CA),is used for displays (shown in thefigure (see Color Plate 20 in theAppendix)). This workbench is large

and permits several individuals tosee the visualization projected abovethe table top in three dimensions.Special glasses are required (seethe figure). The images are greatlyenlarged so that a novice can seedetails readily. The images can thenbe reduced in size to attain a moretrue-to-life size for further practice.This workbench will be used asinteractive, VE tools are developedfor training and planning purposes.Also, displayed images can be sentto remote sites over a network. Thegoal is to have interactive displays sothat researchers and surgeons atremote sites can see identical three-dimensional (3-D) images andinteract with them.

In the Biocomputation Center,unique software has been developedthat permits detailed, 3-D recon-struction of the face and skull ofpatients from computerized tomog-raphy (CT) scans. The VisibleHuman Dataset provided by theNational Institutes of Health wasused to reconstruct the face andskull of a 57-year-old female. In thereconstruction of the face, even tinywrinkles around the mouth can beseen, and deeper wrinkles and thetexture of the skin are realistic.Because of the level of detailpossible, a laser scan to record theface prior to surgery is no longerneeded. The images are renderedwith high fidelity.

The face and skull of an infantpatient was generated from format-ted CT scans in about 20 minutesusing the newly developed softwareand a Silicon Graphics Onyx RE2workstation. The infant had prema-ture closure of a skull suture on theright and of part of the anteriorfontanelle (commonly known as the

“soft spot”). The images of the skullclearly show the extent of fusion ofthe bones. Without surgical interven-tion, the right side of the head wouldnot grow properly, the head and facewould be deformed, and the brainwould be compromised. Because ofthe high fidelity of the viewedimages, surgeons have declared thesoftware ready to use as a diagnostictool. The goal is to have even morecomplex reconstructions completedwithin 15 minutes, or less, making itpossible for doctors in emergencyrooms to have a patient scanned andsee the trauma in 3-D within min-utes. In addition, work is beginningthat will make it possible to port thesoftware to less expensive worksta-tions, promoting wider availability ofthe technology.

A necessary part of the softwaredevelopment is the ability to cut out,to remove, and to insert pieces ofbone elsewhere, then to computa-tionally restore the soft tissues so thatthe new face can be molded to thenew skull for viewing prior tosurgery. Software has been devel-oped to do this using a model gridsystem. The software will be incor-porated for use with an actual skullas the next step in software develop-ment. The software will be generallyapplicable, for example, in recon-structive surgery utilizing skin torecreate a breast in a mastectomypatient.

The value of the training aspectsof the technology should not beunderestimated. It takes as many as20 years to train a highly skilledcraniofacial reconstructive surgeon.If training in a simulator reduces thisamount by half, 10 productive yearswill be added to a surgeon’s profes-sional life. Furthermore, use of

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simulator technology greatly reducesthe cost of training. It is cheaper topractice on a computer than toparticipate in surgery on a patientand learn in this prolonged way.Also, new approaches to surgerycan be quickly incorporated into asimulation to increase capability innew surgical techniques.

The VE technologies that arebeing developed will reduce medi-cal costs, shorten the time necessaryto train surgeons, and permit betterpreplanning of surgery. They alsowill improve the quality of life forthe patient by producing a betteroutcome when surgery is first carriedout. As these beneficial VE technolo-gies are transferred to the public,NASA also benefits from theseapplications that are useful to theHEDS Enterprise and to long-termspaceflight.

Point of Contact: M. Ross(650) [email protected]

Noninvasive Estimationof Pulsatile IntracranialPressure Using UltrasoundToshiaki Ueno, Richard E. Ballard,John H. Cantrell, William T. Yost,Alan R. Hargens

Exposure to microgravity causesa blood shift toward the head thatmay elevate intracranial pressure(ICP). As widely observed in patientswith brain tumors or hemorrhage,elevation of ICP may cause head-ache, nausea, or vomiting. Theseconditions strongly suggest thatelevated ICP in microgravity may


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cause or exacerbate similar symp-toms during spaceflight. In addition,recent clinical reports suggest thatelevated ICP impairs regulation ofblood flow in the brain and normal

neural activity. Consequently, ICP isa critical parameter for understand-ing physiologic adaptation tomicrogravity. However, the magni-tude and time course of altered ICP

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are still unknown, primarily becauseof the invasiveness of currentlyavailable techniques.

A new ultrasound device tomeasure skull movements that occurwith altered ICP has been developedand refined. The principle of thisdevice is based upon pulse phaselocked loop (PPLL), which enablesthe detection of changes in distanceon the order of micrometers betweenan ultrasound transducer on one sideof the skull and the opposite innersurface of the cranium. Although theskull is often assumed to be a rigidcontainer with constant volume,many researchers have demonstratedthat cranial bones move in associa-tion with changes in ICP. In thetypical operation, the instrumenttransmits a 500 kilohertz ultrasonictone burst through the cranium via a

transducer placed on the head. Theultrasonic wave passes through thecranial cavity, reflects off the innersurface of the opposite side of theskull, and is received by the sametransducer.

In the first experiment, changesin cranial distance in three cadavera(ages 85–90) were measured withthe ultrasound device, while pulsa-tile changes in ICP were generatedby infusing saline into the lateralventricle. To correlate the non-invasive measurement with ICPdirectly, a fiber-optic, transducer-tipped catheter was inserted into theintracranial space. In the secondexperiment, changes in cranialdistance in six healthy volunteers(ages 18–31) were measured whilethey were placed in 60 degree,30␣ degree head-up tilt, supine, and

10 degree head-down tilt positions.ICP was not measured directly. Inboth of the experiments, an ultra-sound transducer was taped securelyto the lateral head above theright ear.

In the cadaver study, frequencyanalysis (fast Fourier transformation)revealed that cranial pulsations wereclearly associated with ICP pulsa-tions (see the first figure). In the tiltstudy, the magnitudes of cranialpulsations were linearly correlated totilt angles as shown in the secondfigure.

The ultrasound device hassufficient sensitivity to detect cranialpulsation associated with cardiaccycles. As previously reported, theamplitude of ICP pulsations isclosely related to intracranialcompliance. In other words, whenintracranial fluid volume andpressure increase, arterial pulsationproduces a higher amplitude ICPpulsation. Increased amplitude ofICP pulsations will be manifested bylarger fluctuations in distance acrossthe skull. Accordingly, by analyzingthe magnitude of cranial pulsations,absolute estimates of ICP duringspaceflight are possible.



Fig. 2. Results of tilt study (n = 6). Amplitudes of pulsatile changes in thePPLL output are shown against the tilt angles. A linear regression line issuperimposed.

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MRI-Compatible SpinalCompression HarnessRichard E. Ballard,Donald E. Watenpaugh,Iwane Mitsui, Klaus P. Fechner,Douglas S. Schwandt, Alan R. Hargens

Sixty to eighty percent of thepopulation of the United Statesexperiences back pain during theirlives. While noninvasive imagingsystems such as magnetic resonanceimaging (MRI) and computedtomography scanners have beenused as diagnostic tools for studyingback pain and orthopaedic injury,these imaging devices requirepatients to lie down, thus eliminatingany effect of axial loading on thebody that occurs in upright posture.As a result, these imaging systemsoften provide diagnostic data oflimited use, particularly to disordersrelated to loading and unloading ofthe spine.

The MRI-Compatible SpinalCompression Harness (a patentrecently filed by NASA Ames) isdesigned to produce gravity-likeaxial compressive loads on the body,thus increasing the effectiveness ofexisting diagnostic imaging systemsfor detecting spinal disorders. Inaddition, the spinal compressiondevice will help researchers studythe physiology and biomechanics ofintervertebral discs and causativemechanisms of back pain in patientson Earth and astronauts in space.

The spinal compression appara-tus is lightweight, compact, andinexpensive, and fits into existingdiagnostic equipment without costlymodifications (see first figure). In itspresent configuration, the deviceconsists of a nonmetallic footplate

connected to shoulder pads, andalternatively to a head cap, by nylonwebbing and elastic cords. Pullingthe webbing through plastic bucklesallows adjustment of cord tension,and thus compression level. Theamount of compression is measuredby nonmetallic force sensors that arecurrently being manufactured by acommercial partner. Alternativefeatures of the device include ahelmet-like headgear with adjustableelastic straps to provide neckcompression, a saddle to distributecompression to the seat, and otherattachments that allow static anddynamic compression of specificbody segments or joints. A space-related benefit of the device includesthe potential to compress the spine

and alleviate back pain in astronautsduring spaceflight, when spinallength increases between 4 to7␣ centimeters.

In a recent pilot study, fourhealthy male subjects (age: 33–52;weight: 72–113 kilograms) werefitted with the spinal compressionharness and placed in supine posturewithin an MRI scanner. Each sub-ject’s spine was imaged withoutcompression (control condition) andagain at 25% and 50% body weightcompression (the lumbar spine bearsabout 50% body weight in uprightposture). Three of the subjectsunderwent an additional compres-sion level of 75% body weight (seethe second figure). Longitudinaldistance between T7/T8 (thoracic

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Fig. 1. Percentage of body weight locally supported during upright posture(left) and supine compression in MRI (right). In upright posture, a gradient ofweight-bearing exists from the head to the feet, whereas the harness for MRIcompresses tissues uniformly between the sites of compression. Thus, loadsare adjusted to the specific tissue to be scanned under load (for example, thelumbar spine typically experiences 50% body weight in upright posture).


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Fig. 2. Side view (a) and front view (b) of a spine during MRI with gradedcompression. Note the increase in curvature with increased load. Thisparticular subject had a slightly bulging disc on the posterior side of L3-L4(third visible disc from the bottom) which was accentuated by compression.BW = body weight.

(a)

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level) and L5/S1 (lumbar/sacral level)discs decreased by 3.2 ± 0.8 milli-meters (mean ± SD) with 25%body weight compression,5.6 ± 1.1 millimeters with 50%body weight compression, and6.8 ± 1.2 millimeters with 75% bodyweight compression. The distancereduction was attributed todecreased disc thickness andincreased spinal curvature.

While further development andvalidation of this technology arenecessary, these results indicate thatthe spinal compression harness iscapable of loading the spine effec-tively during supine MRI, and thusmay be a valuable tool for studyingeffects of gravity-like loads on thespine. Previously this capability hasnot been available to researchers orclinicians.


Near-InfraredSpectroscopy to MonitorForearm MuscleOxygenationGita Murthy, Alan R. Hargens

Muscle pain can be caused byrepeated and constant exertion of aspecific muscle. Such exertion mayincrease muscle pressure, reduceblood flow and muscle oxygenation,and cause muscle fatigue and pain.Low levels of prolonged musclecontraction of the forearm musclesare common in many work settingsand may cause fatigue. Crewoperations in the Life Sciences


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Glovebox on the Space Station isone such work environment. Thepurpose of this study was to deter-mine whether forearm muscleoxygenation decreases significantlyat low levels of contraction. Ninemale and female subjects partici-pated in the study. Each subject wasseated as shown in the first figure.

Muscle oxygenation wasmeasured noninvasively using anear-infrared spectroscopy tech-nique. The spectroscopy probe was

placed over the forearm muscle andgently secured with an ace wrap.Subjects were asked to contract theirforearm muscle maximally threetimes. After 1 minute of data collec-tion during relaxed posture, subjectscontracted their forearm muscleonce again for 1 minute, during fourdifferent load applications (randomlyordered). Loads were imposed byweights that were placed on theknuckles and allowed the subjectsto work at 5, 10, 15, and 50% of

maximum voluntary contraction. Atthe end of the minute, the load wasremoved and a 3-minute recoveryperiod followed. At the end of theprotocol, with the spectroscopyprobe still in place, subjects wererequired to exercise their forearmsto exhaustion such that very littlemuscle oxygenation was recorded.This procedure is necessary to obtaina functional zero level for eachsubject. The data were normalizedto a relative scale between thephysiologic minimum (0%) estab-lished during the exhaustive exerciseand the spectrophotometer outputduring relaxation (100%).

After 35 and 40 seconds ofcontraction, muscle oxygenationleveled off at below baseline levelsand remained at that level through-out the 1-minute contraction period.Muscle oxygenation decreased from100% during rest to 89 ± 4% (SE),81 ± 8%, 78 ± 8%, and 47 ± 8% at5, 10, 15, and 50% maximal forearmcontraction, respectively (see thesecond figure). Muscle oxygenationdecreased significantly at 10, 15,and 50% of maximal contractioncompared to resting values.

This study shows a significantreduction in muscle oxygenationeven at levels as low as 10% maxi-mal contraction. Muscle deoxygen-ation during muscle contraction mayplay an important role in the devel-opment of muscle fatigue and painassociated with repetitive tasks,especially in confined environmentssuch as in a glovebox. There are nosimple, easy to use instruments thatcan noninvasively measure muscleoxygenation in deep and superficial

Fig. 1. Subject posture during the study. The inset shows the spectroscopyprobe that measures muscle oxygenation.


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working muscles. Thus, the spectros-copy device may provide an impor-tant tool to study muscle fatigue andpain and to improve the designs ofworkstations in space.


BIONA 1—Blood Flow IonAnalyzerJohn W. Hines, Christopher J. Somps

Liver support systems willbenefit from continuous monitoringand control of the ion concentrationsof processed blood plasma. Tomeasure the concentrations of ionsin flowing blood plasma, a proto-type, computer-controlled dataacquisition system, the “Blood FlowIon Analyzer” (BIONA 1), has beendesigned. BIONA 1 monitors plasmaion concentrations, displays them asa function of time, and saves thedata to a file for later analysis. Thesensors are miniaturized, catheter-type, ion-selective electrodes that

have membranes selective to onlyone ionic species. Since the porcineliver cells decrease the plasmacalcium over time, requiring theaddition of Ca2+-enriched buffers,the initial ion of interest is Ca2+.Monitoring the pH and temperatureof the blood plasma is also desiredand can be implemented with futureprototypes.

To measure concentrations withion-selective electrodes, a referenceelectrode that provides a concentra-tion independent potential isneeded. The potential of the ion-selective electrode (indicatorelectrode) depends on the concen-tration of the ion for which it isselective. The difference betweenreference and indicator potential canthen be related to the ion concentra-tion; a process called calibration.Ion-selective electrodes need to becalibrated before the first use andrecalibrated after certain periods oftime to minimize the amount of errorgenerated by drift and changes insensitivity (potential change perdecade change of concentration).

The BIONA 1 system prototypeallows semiautomatic electrodecalibration. Computer-controlledsolenoid valves are used to tempo-rarily reroute blood plasma awayfrom the sensor flow path to abypass flow path during calibration.One end of the sensor path, its inlet,is then connected to a syringe with acalcium chloride buffer solution, andthe other end, to a waste container.This allows injection of buffersolutions for calibration withoutcontaminating the blood plasmawith buffer. After the buffers havebeen injected and calibration isfinished, the inlet of the sensor path

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is reconnected to the blood plasmaflow while its outlet is still routed tothe waste container. This results inthe removal of buffer solution fromthe sensor path by the blood plasmaflow. After a few seconds (flow-ratedependent), all buffer has beenreplaced by plasma. The sensoroutlet is then switched back and theelectrode tube is completely recon-nected to the blood plasma flow.The prototype is currently limited toa plasma flow rate of approximately100 cubic centimeters per minute.

The electrode signal is amplifiedby a high-input impedance amplifierand acquired by a data acquisitionPCMCIA card and a laptop com-puter. The same card also outputs

digital signals to control (turn on/off)the solenoid valves.

The solenoid valves require a12-volt DC power supply (at least6␣ watt) that is provided by a walltransformer. The amplifier circuit ispowered by two AAA batteries forisolation purposes. To reduce theelectromagnetic interference withthe sensor signal, the box is copperclad to provide shielding. Shielding,however, is only effective if the boxis grounded, which can be accom-plished by connecting the box witha ground wire to earth ground (forexample, from an outlet). A sche-matic of the BIONA 1 system isprovided in the figure.

This technology developmentrepresented a diverse collaborativeeffort between researchers andtechnologists at the Center forEmerging Cardiovascular Technolo-gies (a National Science Foundation-sponsored program managed fromNorth Carolina State University),and a team at the University ofNorth Carolina at Chapel Hill andother affiliates in the ResearchTriangle, and at Case WesternReserve University in Cleveland,Ohio. A prototype Sensor Array formonitoring physiological ions in ahepatic bioreactor was demonstratedin a joint development activity withthe Department of Surgical Researchand the Liver Support Group atthe Cedars-Sinai Hospital inLos␣ Angeles, California.

Point of Contact: J. Hines(650) [email protected]

Intelligent Controller forNeurosurgeryRobert Mah

In preparation for neurosurgeryto remove tumors, magnetic reso-nance imaging (MRI) scans areusually taken to locate the tumorand its positional coordinates.However, during the surgicaloperation to access the tumor, thebrain swells and the location of thetumor shifts. As a result, the neuro-surgeon must rely on experience tosearch for the tumor interface usingsurgical tools and tactile feedback.(Brain tumors typically have a

Blood plasma supply

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Fig. 1. Blood Flow Ion Analyzer (BIONA 1) system diagram.


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different density than normal braintissue). During this procedure, anartery can accidentally be severedby the surgical tool which can leadto death.

A simple robot that can “learn”the physical characteristics of thebrain may give surgeons moreprecise control of surgical instru-ments during delicate brain opera-tions. The procedure utilizes arobotic smart probe that “learns”the brain’s characteristics by usingneural net software. The probe,equipped with tiny sensors, entersthe brain, gently locating the edgesof tumors while preventing damageto critical arteries. Potentially, theneurocontrolled robot, making slow,very precise movements during anoperation, will be able to “feel”brain structures better than anyhuman surgeon.

This research has contributed tothe design of an intelligent robot thatcan improve the safety, accuracy,and efficiency of neurosurgery. Thistechnology is expected to havedirect spinoffs to the general field ofsurgery. In FY96, the NASA/StanfordNeurosurgical ComputationalTestbed was developed (see thefigure). World-wide press coverage(major television stations, majornewspapers, and radio stations) wasreceived and an invention patent ispending.

Point of Contact: R. Mah(650) [email protected]

Fig. 1. Robotic neurosurgical hardware testbed.


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Center for HealthApplications of AerospaceRelated Technologies(CHAART)Byron Wood, Louisa Beck, SheriDister, Brad Lobitz

The Center for Health Applica-tions of Aerospace Related Tech-nologies (CHAART) was initiated atthe beginning of FY95 by NASAHeadquarters’ Life and BiomedicalSciences and Applications Division(Code UL), within the Office of Lifeand Microgravity Sciences andApplications. The goal of CHAART isto promote the application of remotesensing (RS), geographic informationsystems (GIS), and related technolo-gies to issues of human health. Fiscalyear 1996 began with the First CyrilPonnamperuma Symposium onRemote Sensing and Vector-BorneDisease Monitoring and Control,held in Baltimore, Maryland, onNovember 28–30, 1995. Thesymposium, hosted by NASA andthe Third World Foundation (TWF),was attended by national healthrepresentatives from Brazil,Cameroon, China, Indonesia,Malawi, Malaysia, Mexico,Myanmar, Namibia, Nigeria,Rwanda, and Zimbabwe. The goalof the symposium was to developRS/GIS-based, health-relatedresearch proposals from Third Worldcountries. The CHAART staff gavetutorials on RS and GIS and ledpanel discussions to define country-specific issues.

As part of the new Memoran-dum of Understanding (MOU)between NASA and the Centers forDisease Control and Prevention

(CDC), the CHAART staff workedintensively with CDC personnel inAtlanta, Georgia, to develop col-laborative projects. As a result ofthese discussions, the CHAART stafforganized and taught two workshopson the uses of RS for public healthapplications. These workshops wereconducted at CDC Headquarters inAtlanta (May 6–7, 1996), and atCDC’s facility in Ft. Collins, Colo-rado (May 27–30, 1996). Recom-mendations for future NASA/CDCcollaboration were generated atthese events. As part of the NASA/National Institutes of Health (NIH)MOU, the CHAART staff also spentthe year working with researchersfunded through the NIH. Theseresearchers received supplementalfunding through a joint NASA/NIHcall, and used these funds to inte-grate RS/GIS into their ongoingresearch on disease. CHAARTdirectly assisted Dr. James Maguire(Brigham and Women’s Hospital atHarvard Medical School), who isstudying leishmaniasis in Teresina,Brazil, and Dr. Rita Colwell (Univer-sity of Maryland), who is studyingcholera in the Bay of Bengal.

In other activities, CHAART alsoworked closely this year with TWFpersonnel to identify 10␣ visitingforeign scientists whose research orjobs involve human diseases. Thesescientists will spend two months atCHAART during FY97 learning howto integrate RS/GIS into their studieson human health. Two of CHAART’sstaff are on the Advisory Board of thePan American Center for Earth andEnvironmental Studies. This center,established at the University ofTexas, El Paso, as a Minority Univer-sity Research Center, was awarded a$6.5 million grant from the Mission

to Planet Earth Enterprise to supportenvironmental research in theSouthwest.

CHAART also provides RS/GISsupport to Dr.␣ Uriel Kitron (Univer-sity of Illinois, Champagne-Urbana),who is funded by NIH to study thedistribution of Lyme disease in theUpper Midwest.

Point of Contact: B. Wood(650) [email protected]

Telemedicine Spacebridgeto RussiaSteve N. Kyramarios

NASA’s newest telemedicineproject, entitled Spacebridge toRussia, is a collaborative effortbetween NASA and the SpaceBiomedical Center for Research andTraining in Moscow, and establishesa testbed to evaluate Internettelemedicine in both operationaland educational settings. The projectconnects the Clinical Hospital of theMinistry of the Interior in Moscowand the Moscow State MedicalSchool sites with Baylor MedicalCenter, Fairfax Hospital, Latter DaySaints Hospital, and Yale MedicalSchool through the multicast back-bone (MBONE).

The goal of this project is toprovide medical telecollaborationand electronic patient recordproduction and review through theInternet. The program will helpNASA develop a permanenttelemedical system that providesmedical support for its astronautsand other personnel involved in the


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joint spaceflight program withRussia. In addition, the experiencegained from this effort will provideinsight into the potential of medicalpractice over the National Informa-tion Infrastructure and the GlobalInformation Infrastructure.

This telemedicine testbed isbetween three clinical hospitals inthe United States (U.S.) (FairfaxHospital, Falls Church, Virginia;Latter Day Saints Hospital, Salt LakeCity, Utah; and Yale University,New Haven, Connecticut) and twomedical centers in Moscow (ClinicalHospital of the Ministry of Interiorand the Space Biomedical Center forTraining and Research at MoscowState University). UNIX-basedSilicon Graphics Inc. multimediaworkstations are located at each siteand are linked to the Internet. Theworkstations incorporate Internettools including a graphical userinterface (GUI) on the World WideWeb, and the MBONE toolset forvideo conferencing. It is estimatedthat several hundred clinical consul-tations will be conducted betweenthe clinical sites in the United Statesand Russia.

In addition to engineering thetechnical architecture, AmesResearch Center has contributed tothe project by providing technicalleadership and implementation inInternet connectivity, motion videoconsultation, and video teleconfer-encing. These capabilities haveenabled telemedicine consultationsin a “grand round” format for uniquecase presentations. In addition, aneducational program organized byBaylor Medical Center in Houston,Texas, is developing a series onrecent advances in cardiologyunder the direction of Dr. Michael

deBakey, the world famous heartspecialist. The educational programincludes live multicast video andweb-based medical imagery.Clinical consultations are preparedat each site using a standard formatthat includes motion video, datatransfer, still photography, and videoteleconferencing capabilities. Casesare made available to the reviewinghospitals through a Web server. Eachsite provides clinical coordination ofthe cases on a rotating basis.

Point of Contact: S. Kyramarios(650) [email protected]

PROGRESS IN IMPROVING SPACE

TRAVEL

Advanced Life Support/Human Exploration andDevelopment of SpaceEnterprise ActivitiesDick Lamparter, Mark Kliss

The Ames Research Center(ARC) Advanced Life Support Branchcarries out research and develop-ment of new technologies that willadvance the human explorationand development of space. Theseactivities will reduce life cycle costs,improve operational performance,promote self-sufficiency, andminimize expenditure of resourcesfor future space exploration. Signifi-cant opportunities for Earth applica-tion of the developed technologiesare available, including:

Atmosphere Regeneration: Dataon the influence of water on the

adsorption of carbon dioxide andtrace contaminants show significantreduction in capacity of sorbents andthe possibility of elution back intothe cabin environment. New materi-als and operating procedures willhelp mitigate this safety problem.New knowledge of adsorptionprocesses has lead to a method ofin␣ situ resource utilization of oxygenfor Mars missions. Experimentallyvalidated, the process is likely tofly on the Mars In Situ PropellantProduction/In Situ Resource Utiliza-tion (ISPP/ISRU) Precursor experi-ment in 2001. The data beingdeveloped on materials have giveninsight into process modificationsthat will reduce power and spacerequirements. This research programsupports contamination aspects offlight experiments.

Recovery of Resources from WasteMaterials: Not currently recycled,human and food wastes are keyelements for advanced life-supportsystems that approach self-sufficiency. Both Supercritical WaterOxidation (SCWO) and incinerationprocessors have been developed andare currently under evaluation. Keyissues being addressed include wastepreparation and process feed andproduct stream cleanup, with aspecial focus on acid gases andother trace contaminants produced.A prototype incinerator will soon bedelivered to the Johnson SpaceCenter (JSC) for evaluation in anextended manned chamber test. TheU.S. Navy has expressed interest inSCWO technology for its potential toreduce hazardous liquids to carbondioxide and water while ships aredeployed at sea.

PROGRESS IN IMPROVING SPACE␣ ␣ TRAVEL

P R O G R E S S I N I M P R O V I N G S P A C E T R A V E L

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Food production: Activity in thisarea is leveraged off prior research.In collaboration with the NationalScience Foundation, a unit toproduce fresh food at the South Poleis being developed. The analysis ofdietary requirements, crop mix, andmulticropping in growth chambershas application to the HumanExploration and Development ofSpace (HEDS) objective of providingself-sufficiency. Experience indealing with crews in remoteenvironments is applicable to NASA.Information generated from thisprogram is being formatted as partof the development of the JSCchambers.

These activities form the basisfor an important technology transferto native communities in Alaskawhere health hazards exist becauseof poor rural sanitation. Code STRhas established cooperative agree-ments with the state, university, andlocal communities to apply theNASA-developed technology andsystems analysis capability towardimproving health, through diets andtreatment of water and solid wastestreams.

Point of Contact: M. Kliss(650) [email protected]

Mir Hardware—SteppingStone to StationBonnie P. Dalton, James Connolly,Gary Jahns, Paul Savage

The Mir program has not onlyallowed the performance of biologi-cal experiments under long-termmicrogravity exposure (for example,90 to 145 days), but also has pro-vided a realistic view of experiencesduring the International SpaceStation program in terms of opera-tions and hardware preparations.In contrast to the Spacelab profiles,in which major flights occurredevery 2␣ to 3 years, Mir flights andthe associated planning, hardware

and experiment development, andpre/postflight processing haveoccurred three times annually andhave typically been initiated noearlier than 1.5 years prior tolaunch. As a result, hardware hasbeen developed very rapidly, withapplications to interim flights aprincipal objective (until theInternational Space Station is fullyfunctional).

During the past 2␣ years, aninsect habitat and a standard inter-face glovebox (SIGB) have beendeveloped for use on Mir. The insecthabitat was built with the assistanceof Lockheed Martin Engineering andSciences Company and othercontract support.


Fig. 1. Microgravity glovebox for Mir.

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The SIGB was designed toprovide a fully enclosed workspacefor the execution of in-flight scienceprocedures. The SIGB utilizes slidingrails and latches adapted from theJohnson Space Center’s standardinterface rack (SIR), allowing it to flyin virtually any existing or futurespace platform. The work surface ofthe unit is approximately 1 squarefoot and the work volume is2.3␣ cubic feet. Bounded by afiberglass shell consisting of fivelayers of epoxy resin, it is finishedwith white urethane for easy clean-ing. Airflow within the unit ismodeled after a laminar flow hood.The air filtration system provides anet negative pressure of 0.1 to0.6␣ inch water with respect toambient. All portions of the SIGBairflow system maintain negativepressure with respect to ambient inall operational modes. The filtrationsystem has been designed to providefull containment of spills for specificchemicals (used in biological fixativepreparations), including Campbell’sFixative, paraformaldehyde, andRussian variant solution. Access foroperation is through attachedgauntlet ports. The SIGB, ready formounting in the Space Transporta-tion Service vehicle, is shown inthe figure.

The insect habitat, known asthe Beetle Kit, was designed for aNASA-5 increment experimententitled “Effects of Gravity on InsectCircadian Rhythmicity” that willstudy the Tenebrionid beetle. Thehardware incorporates an automatedcircadian timing system (CTS). Sinceprevious spaceflights have shown anotable effect on the CTS of both

vertebrates and invertebrates, it isanticipated that the ability to per-form long-term measurements onMir will greatly enhance the scien-tific community’s knowledge of thissubject. The Beetle Activity Module(BAM), the hardware housing theinsect and the timing system, is anadaptation of an existing item ofRussian hardware with expandedcapabilities. Housing 32 beetles, theBAM is self-contained, and includesboth a treadmill and a timing system.Food consists of a small quantity ofdry oatmeal. Movement of a beetleon the treadmill indicates theinsect’s activity during portions ofits circadian rhythms. Data collectedfrom the flight experiment and fromground-based centrifuge studies atAmes Research Center will helpdetermine if the CTS exhibitsadaptation during long-term expo-sure to altered gravitational fieldsand whether that exposure changesthe sensitivity of the CTS to flight.

In summary, Ames’ participationin the Mir program resulted in thedevelopment of important hardwareused for long-duration investigationsand the methodology for rapidlybuilding and qualifying the hard-ware. Additionally, Ames’ participa-tion has served as a vital educationalstepping stone toward ensuring thesuccess of activities onboard theInternational Space Station.

Point of Contact: P. Savage(650) [email protected]


Wireless NetworkExperiment for SpaceShuttle/MirRichard Alena

The Wireless Network Experi-ment (WNE) was a risk-mitigationexperiment designed to demonstratethe feasibility of using wirelessnetworks aboard the InternationalSpace Station. The customer was theShuttle/Mir Science Program at theJohnson Space Center (JSC), which isunder the Space Station Program.The WNE consisted of a set of threecomputers that could communicatevia the wireless radio networksystem, as shown in the figure. Anetwork monitor program graphednetwork throughput in real time asthe computers were moved throughthe habitable volume. This experi-ment was successfully conductedonboard both the Space Shuttle andMir Space Station during the dockedspace transport system-76/Mir 21flight.

The current International SpaceStation data system baseline doesnot provide adequate support forpayloads and onboard computersystems. Adding additional cablednetwork resources is prohibitive interms of cost and weight. A wirelessnetwork allows portable computingresources to be brought up to theSpace Station and installed withminimal effort and, at low-cost,support a significantly augmenteddata processing capability forpayloads and crew.

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The WNE was conducted inMarch 1996. Demonstration of thenext-generation (Web-based) datasystem concept to NASA and JSCastronauts and engineering managerswas made in May 1996. The post-flight testing and preliminary reportwere completed in August 1996.

Point of Contact: R. Alena(650) [email protected]

Engine Diagnostic FilterSystemTarang Patel

The project objective was todevelop posttest data analysis toolsfor potential deployment as real-timeand in-flight instruments for the nextgeneration rocket engines for spacevehicles. Analysis was made on theexhaust plume data collected fromthe Space Shuttle main engines. Theanalysis capability is to give indica-tions of engine erosion and itspotential source inside the motor.

The real-time analytic capabilityis unique in its ability to identify theprincipal eroding metal speciesunder way in an engine duringengine operation. Such healthmonitoring activity can be used toshut down an engine test prior to apotential catastrophic failure. Thisstep could lead to a possible in-flightcapability, under research, whichwould be used for onboard diagnosisfor health management, and couldrepresent a safety check for thespace vehicle crew. A much moreimmediate benefit of the posttestanalysis is that it provides engineers,


Fig. 1. Schematic of the Wireless Network Experiment (WNE) system.

Powercable

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involved in engine tear-downactivity following a test, a realindication of whether such anexpensive task is necessary.

This project was the world’sfirst use of plume spectroscopy toproduce realistic, quantified esti-mates of metal erosion from a rocketengine. During recent routine testingof a main Space Shuttle engine at theStennis Space Center, the analysistools coupled to data from a diag-nostic instrument were able todetermine metal erosion taking placeand pinpoint the event of a cata-strophic failure. The methods usedin the analysis were even able toextract silver and copper lines,despite the fact that they wereswamped in the rich hydroxylgrouping (OH) structure of thespectrum.

Point of Contact: T. Patel(650) [email protected]

Formal LightweightApproaches to Validationof RequirementsSpecificationsSteve Easterbrook

The objective of this researchwas to evaluate the use of formalmethods as a tool for independentverification and validation (IV&V) ofsoftware requirements specifications(SRS) for spacecraft flight software.Formal methods allow an IV&V teamto test SRS for properties such asconsistency, completeness, safety,and correctness. The research

focused on lightweight methods,which can be applied to smallchunks of a specification without asubstantial investment in translatingentire specifications into mathemati-cal notations.

A series of case studies wasconducted, applying formal model-ing techniques to ‘live’ projects, sothat the results can be fed back intothe project in time to be of addedvalue. The case studies were chosenin response to real needs on existingprojects; for example, where anadditional level of assurance of thecorrectness of the requirements wasneeded, over and above that obtain-able through existing methods. Thecase studies completed in the pastyear related to the InternationalSpace Station. A range of differentformal methods was applied,including software cost reduction,the prototype verification system,and the model checker softwareprocess improvement network(SPIN). In each case the amount ofeffort required to apply the methodwas examined, along with the typesof benefits gained. This evaluationwas mainly qualitative, as thebaseline metrics do not exist fordetailed quantitative comparisons.

The analysis conducted duringthe case studies provided a signifi-cant addition to the IV&V performedon the Space Station SRS. A majorcase study examined the require-ments for the fault detection, isola-tion, and reconfiguration (FDIR) forthe main communications bus onthe space station. This studyinvolved translation of the originalprose requirements into a formal,tabular notation, and analysis of theresulting model for consistency, for

key static properties, and for correctdynamic behavior. The figure showsan analysis of the timing behavior ofthe FDIR requirements using theSPIN tool.

The formal methods allowedthe IV&V team to quickly identifynumerous weaknesses in theserequirements, including ambiguoususe of terminology, missing require-ments, and inconsistencies in thetiming requirements. These problemswould normally not be detecteduntil later in the developmentprocess, at which point the costs tocorrect them are significantly higher.

Results indicated that the maineffort involved in applying theformal methods is in translating theprose requirements into the formalnotation. However, this effort isconsistent with the level of effortnormally applied to performingIV&V on critical functions. Incontrast, the ability to spot errorsand omissions is greatly improved,as over half the issues identified inthe formal analysis could not bedetected during the requirementsphase using existing methods.Hence, formal methods provide acost-effective approach to analyzingrequirements, provided they can befocused.

Formal methods have not yetgained widespread acceptance bysoftware practitioners. Part of theproblem has been an emphasis onadopting a baseline formal specifica-tion, from which to prove that designand implementation are correct.This project has demonstrated thata more realistic approach is to useformal methods for small pieces ofmodeling, especially during the early


134 P R O G R E S S I N I M P R O V I N G S P A C E T R A V E L

Fig. 1. A screensnapshot fromthe SPIN tool,showing theFDIR system(center)interacting withother subsystems(the clock, a testharness, and thehardware itcontrols). Thisanalysis allowsthe analyst toconfirm that thesoftware willbehave in theintended fashioneven before it iswritten; that is,based solely ona statementof therequirements.

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requirements stages, to answerquestions that cannot be addressedin other ways.

Point of Contact: S. Easterbrook(304) [email protected]

ASTRONAUT HEALTH/COUNTERMEASURES

Autogenic-FeedbackTraining as a PotentialTreatment for PostflightOrthostatic IntolerancePatricia S. Cowings,William B. Toscano

The goal of this research is todetermine if human subjects canlearn to voluntarily control bloodpressure increases during a gravito-inertial stimulus (for example, tilttable), and to determine the mecha-nisms by which such control iseffected. The training method used,Autogenic-Feedback TrainingExercise (AFTE), was initially devel-oped as a treatment for motionsickness. It involves teachingsubjects to control voluntarily up to 20 of their own physiologicalresponses simultaneously. In supportof the present study, cardiovasculardynamics (derived from impedancecardiography) were measured anddisplayed to test participants in realtime. These measures included:cardiac output, stroke volume, andan estimate of vagal tone. Tests arein progress; this report outlines theresults obtained to date.

Baseline data were collected oneach subject during supine, head-uptilt, and head-down tilt conditions.

Subjects were given two tests, each50 minutes long, one test before andone test after AFTE. Physiologicaldata were continuously recordedduring both tests with the Autogenic-Feedback System-2 and impedancecardiography. The protocol for thesetests is outlined as follows:1. Supine resting 10 minutes

baseline2. Head-up tilt at 10 minutes

50 degrees3. Supine resting 10 minutes

baseline4. Head-down tilt at 10 minutes

–30 degrees5. Supine resting 10 minutes

baselineEach subject received 6 hours

of AFTE, which was administered intwelve 30-minute sessions (withsubjects sitting; that is, nontiltconditions). Following a 6-minutepretest baseline, each 30-minutetraining session was divided intoten 3-minute trials, during which

subjects were instructed to alter-nately increase and decreaseresponse levels (for example, heartrate accelerations and decelerations,peripheral vasodilatation andconstriction, etc.). A 6-minute restingbaseline was also collected aftereach session (total 42 minutes).

The purpose of these trainingsessions was to provide subjectswith the ability to recognize bodilysensations associated with bothincreases and decreases in theirphysiological response levels and,with practice, to improve their skillin controlling these responses.Subjects eventually learn to maintaintheir physiological response levels ator near their own resting baselinelevels and improve their toleranceto environmental stressors (forexample, tilt table, conditions ofmicrogravity, etc.).

The first figure shows a subjectin the head-down tilt position. The

ASTRONAUT HEALTH/␣ ␣ COUNTERMEASURES

Fig. 1. Subject during 30-degree head-down tilt.

A S T R O N A U T H E A L T H / C o u n t e r m e a s u r e s

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second figure shows physiologicalresponses of cardiac output (topchart) and heart rate and bloodpressure (bottom chart), before andafter AFTE. This subject made asignificant increase in both heart rateand cardiac output in response tohead-up tilt (minutes 11 through 20)after eight AFTE sessions. There wasno observable change in cardiacoutput during tilt before training.

The third figure shows thephysiological data of one subjectduring AFTE sessions four (afteralmost 2 hours of training) and eight(after almost 4 hours of training). Thedata shown include finger pulsevolume, respiration rate, heart rate,skin conductance level, cardiacoutput, stroke volume, centralvolume (actually thoracic imped-ance), and an estimate of vagal tone(calculated by Fast Fourier Transformin real time). Following the 6-minutebaseline, subjects were instructed toproduce arousal responses (constric-tion of finger blood volume, heart-rate and skin-conductance-levelincreases) but not to modify respira-tion or to contract muscles. Moreconsistent control of finger pulsevolume was apparent during sessioneight than during session four—as the subject makes the desiredresponse at 3-minute intervals.Respiration was recorded to showthat the subject was neither hyper-nor hypoventilating (by sessioneight) to influence other responsechanges. By session four, both heartrate and skin conductance levelshow evidence of learning thatremained consistent through sessioneight. Note, however, that learnedcontrol of cardiac output, strokevolume, and vagal tone was not

Fig. 2. Physiological responses to tilt before and after AFTE.


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Fig. 3. Physiological responses during AFTE sessions four and eight. Note: Following a 6-minute resting baseline,subjects are instructed to produce alternating arousal (that is, constriction of blood flow to the fingers, heart-rate andskin-conductance-level increases) and relaxation responses (that is, vasodilation of fingers, decreases in heart rateand skin conductance level) at three 3-minute training trials, showing for the first time that these parameters may besubject to learned, voluntary control.


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apparent until session eight, suggest-ing that AFTE practice is associatedwith observed response changes.Central volume was also modulatedwith instruction (that is, at 3-minuteintervals) more consistently aftereight sessions.

These data represent the firstindication that these measures ofcardiac dynamics are subject tovoluntary control through learning.They show that AFTE methods mayyield a powerful, potential counter-measure for postflight orthostaticintolerance that may supplementexisting exercise routines utilized bycrewmembers.

Point of Contact: P. Cowings(650) [email protected]

Exercise for Long-Duration SpaceflightDonald E. Watenpaugh,Richard E. Ballard,Karen J. Hutchinson,Jaqueline M. William, Andrew C. Ertl,Suzanne M. Fortney, Lakshi Putcha,Wanda L. Boda, Stuart M. C. Lee,Alan R. Hargens

Adaptation to microgravity leadsto cardiovascular and musculoskel-etal deconditioning to normal Earthgravity. Specific problems includemuscle atrophy, bone demineraliza-tion, reduced neuromuscularcoordination, and postflight reduc-tion of orthostatic tolerance andupright exercise capacity. Presently,exercise protocols and equipmentfor astronauts in space are unre-solved, although recent calculationssuggest that all exercise in space to

date has lacked sufficient loads tomaintain preflight musculoskeletalmass. Although treadmill exercisewith bungee cords (about 2 hoursper day) is the most commonexercise for cosmonauts during long-duration Mir missions, biomechani-cal loads on musculoskeletal tissuesof the lower body are only about60␣ to 70% of those present on Earth.Theoretically, an integrated counter-measure for extended exposure tomicrogravity should combine highloads on the musculoskeletal systemwith normal regional distributions ofblood pressure and stimulation ofnormal neuromuscular locomotorpatterns.

Lower-body negative pressure(LBNP) exercise is an integratedcountermeasure that may prevent

bed rest- and microgravity-induceddeconditioning by simulatinggravity. (See the figure.) The LBNPexercise device consists of a verti-cally oriented treadmill within apartial-vacuum chamber that issealed around the subject’s lowerbody. For use on Earth, supinesubjects are supported by a suspen-sion system of cables and pulleys.Suction pressure is used to pullblood and other body fluids awayfrom the heart (thus reproducingnormal upright blood pressuregradients) while simultaneouslycreating a gravity-like footwardforce.

In a recent study, it was hypoth-esized that daily LBNP exercisemaintains cardiovascular andmusculoskeletal conditioning during

Gx

Gz(LBNP suction force)

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Fig. 1. Treadmill reaction force to generate body weight in supine postureequals the product of the cross-sectional area of the flexible waist seal andthe suction pressure within the LBNP chamber. With exercise, inertialreaction forces against the treadmill are added to the static force.


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6-degree head-down bed rest. Sevenhealthy male volunteers acted astheir own controls, such that theirresponses to 2 weeks of bed restwith daily supine LBNP treadmillexercise (40 minutes of walking andrunning at 1.0 to 1.2 body weights offootward force) were compared totheir responses to 2 weeks of bedrest with no daily exercise. The2-week bed rest sessions wereseparated by 10 weeks.

Forty minutes per day of LBNPexercise preserved upright exercisecapacity during 2 weeks of bedrest. Subjects’ time to volitionalexhaustion during their individual-ized treadmill tests decreased1.72␣ minutes on average (10%,p < 0.05) after bed rest with no dailyexercise; daily LBNP exercise duringbed rest maintained exercise toler-ance time at pre-bed rest levels.Daily LBNP exercise also maintainedpeak upright oxygen consumption(VO2) at pre-bed rest levels (pre-bedrest: 59.5 ± 3.2 milliliters/minute/kilogram; post-bed rest: 56.4 ± 3.4).Mean peak VO2 decreased sig-nificantly from 57.6 ± 2.6 to49.8 ± 1.5 milliliters/minute/kilo-gram after bed rest with no exercise.Sprint speed from a standing startwas maintained at pre-bed rest levelswhen daily LBNP exercise accompa-nied bed rest (pre-bed rest:5.5 ± 0.2 meters/second; post-bedrest: 5.2 ± 0.3). However, bed restwithout daily LBNP exercise signifi-cantly reduced sprint speed from5.5␣ ± 0.2 to 4.6 ± 0.3 meters/second, below pre-bed rest controllevels.

In conclusion, LBNP exerciseimproves upon current spaceborneexercise technologies by supporting

cardiovascular and musculoskeletalfitness while reducing the durationof astronaut exercise sessions.


Keiser SX-1 VariableResistance Exercise DeviceJennifer Pedley, Anthony Artino,Richard Ballard, Alan R. Hargens

Muscle atrophy and decreasedbone density are problems associ-ated with extended exposure tomicrogravity. Therefore, it is vital forastronauts to exercise during long-duration spaceflight to reduce theseadverse physiological changes. Incollaboration with Ames ResearchCenter and Palo Alto VeteransAdministration Rehabilitation

Research and Development Center,the Keiser SX-1 resistance exercisedevice was developed to preventmuscle atrophy and bone weakness.Two pneumatic pistons providevariable and high resistance for thelower-body exercises, whereas asingle piston allows resistanceexercises for the upper body andspine. When performing the exer-cises, the user is secured by aharness to provide muscle isolationand proper positioning (see the firstfigure). The device includes anadjustable monitor that providesfeedback information such as force,work, and power. Other featuresinclude strength and cardiovascularmodes represented on the monitor.In the strength mode, the monitordisplays the number of repetitionsand the angle of the upper-bodyexercise levers. The cardiovascularmode conveys to the user repetitionsper minute, total time of the exercise

Fig. 1. The Keiser SX-1 in an unfolded configuration.


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for upper and lower body, andgraphic indicators to represent therange of motion. The Keiser SX-1is designed to fit into a standardSpace Station rack. The total weightof the device is 120 kilograms(265␣ pounds), but the weight can bereduced to 80–100 kilograms usingaluminum.

All exercises are performed inone or two positions by using thefour buttons located on thehandgrips. Two thumb buttons oneach handgrip are capable ofadjusting (1) the amount of resis-tance to the upper and lowerextremities; (2) the leverage from apulling to pushing exercise (that is,pulldown to a chest press); and(3)␣ the range of motion for armsfrom 0 to 70 degrees (that is, row toshoulder press exercise). Maximumand minimum resistance values forthe lower-body range from 1,500 to100 Newtons and for the upper bodyfrom 1,000 to 50 Newtons. At anydesignated time, the user can adjustthe resistance and exercise.

A user can perform resistanceexercises from supine and pronepositions. These exercises include:(1) bilateral chest press for strength-ening the pectoralis major, anteriordeltoids, and triceps; (2) bilateralrow for strengthening the latissimusdorsi, rhomboids, and biceps;(3)␣ bilateral shoulder press, supineand/or prone position for strengthen-ing the deltoids and triceps;(4)␣ bilateral lat pull-down, supineand/or prone position for strengthen-ing the latissimus dorsi and biceps;(5)␣ bilateral or unilateral leg press forstrengthening the gluteals, quadri-ceps, hamstrings, calf muscles, and

lower back postural muscles; and(6)␣ bilateral or unilateral hip flexion.In addition, many of the aboveexercises produce spinal loading thatmay help reduce back pain due tospinal lengthening in microgravity.

In a comparison evaluation witha standard supine leg press (SLP)device, the SX-1 demonstratedsimilar thigh muscle electromyo-graphic (EMG) activities duringconcentric and eccentric exercises(see the second figure). With regard

to the calf muscles, gastrocnemiusEMG activity was greater with theSX-1 than the SLP, while soleus EMGactivity was similar or slightly lowerwith the SX-1 than the SLP. Theseresults indicate that the Keiser SX-1is capable of loading thigh and calfmuscles in a manner similar to aconventional leg press device usedfor ground-based exercise.

Presently, cardiovascularmachines are emphasized on theSpace Shuttle; however, strength

Fig. 2. Average thigh muscle electromyographic (EMG) activity in 11subjects for the concentric (Con) and eccentric (Ecc) phases of contractionduring a 10-repetition maximum leg press exercise using the Keiser SX-1and conventional supine leg press (SLP). In general, EMG activities weresimilar between the SX-1 and SLP, with the exception of concentriccontractions of the vastus medialis and rectus femoris. This difference isprobably related to a lesser load placed on these muscles using a variablepneumatic resistance for the SX-1 as compared to a constant weightfor the SLP.

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training devices are an exception.Exercising on a variable-resistancedevice during spaceflight may beeffective in decreasing the detrimen-tal physiological effects caused byexposure to microgravity. Keiser SX-1has the ability to combine cardiovas-cular and resistance training as wellas spinal loading during exercise.With an appropriate high-resistancetraining protocol, users may beable to maintain muscle size andstrength as well as bone density. TheKeiser SX-1 represents an importantadvance toward this goal.


Dehydration at AirlineCabin AltitudeJohn E. Greenleaf, Peter A. Farrell,Helmut Hinghofer-Szalkay

A contributory factor for thejet-lag syndrome in humans is totalbody dehydration, or hypohydration(see first figure), which is manifestby a reduction in plasma volume(hypovolemia). Exposure to pro-longed chair-rest confinement andpossibly to moderate altitude (alt.),as occurs in passenger airline cabins,could facilitate this dehydration.The purpose of this study was to

Fig. 1. Factors affecting in-flight hypovolemia.

determine if rehydration drinks(AstroAde (AA), Performance 1 (P1),or water (H2O)) could amelioratethe hypovolemia in 10 young men(21 to 30␣ years old, weighing 62 to101␣ kilograms) sitting (with lightactivity) for 12 hours at 2800 meters(9184 feet, 539 millimeters Mercury)in an altitude chamber.

After the subjects rested for10␣ hours in the chamber andconsumed three normal meals(2850␣ kilocalories, 1400 milliliterswater), their plasma volumedecreased significantly (p < 0.05)by 9.0% (AA, alt.), 6.2% (P1, alt.),7.4% (H2O, alt.), and 9.0% (H2O,

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ground). (See second figure.) Themen then drank AA, P1, or H2O(12␣ milliliters/kilogram body weight,948 milliliters at 16 degrees Centi-grade). At 90 minutes (hour 120 afterthe 30-minute drinking period),plasma volume had increased by8.3% (AA, p < 0.05), 2.8% (P1, notsignificant), –0.9% (H2O, alt., notsignificant), and 0.8% (H2O, ground,not significant).

These data indicate that signifi-cant dehydration and hypovolemiaoccur with adequate food and fluidintake during moderate (12-hour)confinement (sitting) at moderatealtitude. Because plasma volumealso decreased on the ground, itappears that confinement, and notthe moderate hypoxia, causes thehypovolemia and hypohydration.


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144

Mission to Planet Earth Enterprise

145

O v e r v i e wNASA’s Mission to Planet Earth

(MTPE) studies the total Earthenvironment—atmosphere, ice,oceans, land, biota, and theirinteractions—to understand theeffects of natural and human-induced, near-term changes on theglobal environment and to lay thefoundation for long-term environ-ment and climate monitoring andprediction. Ames Research Centersupports the MTPE Enterprise byconducting research and developingtechnology to expand the knowledgeof Earth’s atmosphere and ecosys-tems. This objective is also one ofthe goals of NASA’s astrobiologyresearch and technology efforts,which are led by Ames. A comple-mentary objective is to apply theknowledge gained to practical,everyday problems and to transferthe technology and knowledge tousers outside NASA. Numerousresearch and technology efforts wereaccomplished during FY96, and theresults address the following goals ofthe MTPE Enterprise:

␣ ␣ • Expand scientific knowledge ofthe Earth‘s environmentalsystem.

␣ ␣ • Enable the productive use ofMTPE science and technology.

␣ ␣ • Disseminate information aboutthe Earth’s environmentalsystem.

The research is particularlyconcerned with atmospheric andecosystem science and with bio-sphere/atmosphere interaction. Keycomponents of the research includethe study of physical and chemicalprocesses of biogeochemicalcycling; the dynamics of terrestrial

and aquatic ecosystems; the chemi-cal and transport processes thatdetermine atmospheric composition,dynamics, and climate; and thephysical processes that determinethe behavior of the atmosphere onthe Earth and other solar systembodies. Of special interest are thedevelopment and application ofnew technologies required to bringinsight to these science topics.Significant contributions were madein three areas: analysis of criticalgaseous emissions, development ofmodels and instruments, andradiation research.

Research highlighted in thisreport includes focus on importantenvironmental concerns related tostratospheric ozone depletion,perturbations in the chemicalcomposition of the atmosphere,and climatic changes from clouds,aerosols, and greenhouse gases.Numerous state-of-the-art instru-ments were flown successfully, andsignificant data were collected forstratospheric and troposphericresearch. For stratospheric experi-ments, the following are included:the Meteorological MeasurementSystem (MMS), which measurespressure, temperature, and thewind vector; and a dual-channeltracer instrument for stratosphericdynamics studies (Argus).

These instruments were flownon the ER-2 aircraft for the AirborneSouthern Hemisphere OzoneExperiment and for the StratosphericTracers Atmospheric Transport(STRAT) study. For troposphericexperiments, instruments were flownon several aircraft to measure carbonmonoxide, nonmethane hydrocar-bons, carbonyls, and reactivenitrogen species. Specifically,

M I S S I O N T O P L A N E T E A R T H E N T E R P R I S E

146

fluxes of important biogenic gasesfrom terrestrial ecosystems werequantified, as were contrails ofsubsonic aircraft and cloud effects(SUCCESS) and tropospheric aerosolradiative forcing (TARFOX).

Technology developments wererealized on two fronts—modelingand instruments. Model develop-ment efforts or simulations based ondeveloped models are presented forthe following phenomena: the effectof gravity waves generated byconvection or stratospheric circula-tion; the effects of climate andlandcover interactions in the borealbiome; soil/atmosphere exchangeof key trace gas species; biomasscombustion and pyrogenic trace gasemissions; seasonal differentiationof microbial methane sources; aknowledge-based, interactive,graphical tool; use of supercomputertechnology in ecosystem simulation;and paleoenvironment studies usingpollen data and leaf area develop-ment. Newly developed instrumentsinclude: a miniaturized, lightweight,tunable diode laser spectrometer; anMMS on the NASA DC-8 aircraft toprovide science-quality state vari-ables and wind data; an airbornedisaster-assessment sensor; a digitalarray scanning interferometer;and a fully automated, 14-channelsunphotometer to fly on remotelypiloted aircraft and other platforms.Also, a new program was created(ERAST) to focus critical technologydevelopment and flight demonstra-tion for remotely piloted vehicles.

Radiation research focuses onphenomena associated with theinteraction of solar radiation with theatmosphere and solar system bodies.The high-resolution infrared spec-troscopy is devoted to basic experi-mental and theoretical research intothe absorption of radiation by gases.The purpose is to determine themolecular spectroscopic parametersneeded for the design and interpreta-tion of field measurement programsrelated to the environment of Earth’sand other planetary and stellaratmospheres. This report alsohighlights experiments conductedwith the Radiation MeasurementSystem and with a new within-leafradiative transfer model.

Using MTPE data and technol-ogy, commercial firms can expandtheir businesses and public-sectormanagers can exercise stewardshipof the nation’s natural resources.The enabling, productive use ofMTPE science and technology isexemplified by numerous accom-plishments including the effects ofland-use change on the methodsand assumptions currently in use toestimate the influence of land coverin Earth’s carbon budgets of thenorthern boreal forest inOregon. Other reported data,analyses, and technologies can beused by researchers who seekanswers to key Earth science ques-tions and by educators who teachEarth sciences.


147

Ecosystem Scienceand Technology

AIRDAS—Use of RemoteSensing for DisasterAssessment andManagementJames Brass, Vincent Ambrosia,Robert Slye

Each year natural disasters inthe United States cause an estimated20 to 50␣ billion dollars in damage.Fires, earthquakes, floods, hurri-canes, and tornadoes destroythousands of structures, devastateresources, raise havoc with transpor-tation and communication networks,and cause loss of life. The manage-ment of these events is costly anddifficult. The consequences of thesedisasters are evident, and they lendthemselves to monitoring, mapping,and assessment by remote sensing.The goal of this applied researchproject, funded by NASA’s Missionto Planet Earth Enterprise and theU.S. Forest Service, is to develop,demonstrate, and transfer thistechnology to value-added compa-nies and the user community. Thedevelopment, based on the AirborneInfrared Disaster Assessment System(AIRDAS), a compact, multispectralscanner designed for quick aircraftintegration and deployment, takesadvantage of technology developedin the Silicon Valley of Californiaand government laboratories, tocollect, analyze, and communicateinformation to disaster managementpersonnel. The research was per-formed in collaboration with EdwardHildum of Sverdrup Technology,

Robert Higgins of SIMCO Electron-ics, Philip Riggan and RobertLockwood of the U.S. Forest Service,and Chien Nguyen of Raytheon.

Recent activity has involved theuser community, the U.S. ForestService, the California Departmentof Forest and Fire Protection, the LosAngeles County Fire Department, theOffice of Emergency Services, andthe Federal Emergency ManagementAgency to develop system require-ments, review present capabilities,and make recommendations forsystem improvements. Majorupgrades to the system, developed tofill user-driven requirements, includeadditional onboard real-time displaycapabilities, a real-time downlinkcapability, and improved userinterface software for data exploita-tion. The system continues to beintegrated on users’ aircraft fordisaster monitoring and assessment.Currently, the system resides onNASA’s Lear 24, but it has alsoflown on P-3s, the Lear 35 and 31,the KingAir 200, and a Navajo.

The system was used in Brazil inFY96 to detect and map deforesta-tion and fire activity, and to flydisaster␣ monitoring missions inCalifornia, New Mexico, andArizona. The system is currentlybeing upgraded to provide higher-resolution datasets and to increasethe telemetry capability.

Point of Contact: J. Brass(650) [email protected]

Bay Area DigitalGeoresourceEdwin Sheffner, Sheri Dister,Don Sullivan

The Bay Area DigitalGeoresource (BADGER) is a coop-erative project among NASA,Lockheed Martin Palo Alto ResearchLaboratory, and a nonprofit organi-zation called the Bay Area SharedInformation Consortium (BASIC).The goal of BADGER, fundedprimarily by NASA’s High-Performance Computing andCommunication Program, is toprovide NASA data and technologytoward development of a system thatwill make digital, geospatial data ofthe San Francisco Bay Area availableover the Internet. BADGER technol-ogy will serve as the basis for anongoing service operated by BASIC.

BADGER contains three opera-tional functions, all of which aredesigned to be performed on theInternet. First, BADGER provides a“clearinghouse” for information onthe nature, location, and cost ofgeospatial data of the Bay Area.Geospatial data contain a distribu-tional component, that is, data thatcan be represented on a map.Geospatial data include, forexample, images of the surface ofthe Earth from ground-based cam-eras to satellite systems, digitizedmaps showing location of roads,parcels, transmission lines, andwater features, and thematic mapsof natural hazards or populationdistributions. BADGER allows usersto locate geospatial data quickly.Second, BADGER provides amechanism for public and privateproviders of geospatial data to

E C O S Y S T E M S C I E N C E A N D T E C H N O L O G Y

ECOSYSTEM SCIENCE AND␣ ␣ TECHNOLOGY

148 E C O S Y S T E M S C I E N C E A N D T E C H N O L O G Y

market data to users. After a user haslocated data of interest, he or shewill be able to place an orderthrough BADGER that will accessthe dataset on the server of the dataprovider, transmit the data to theuser’s machine, notify the user andthe provider of completion of thetransaction, and bill the user for thedata delivered. Lastly, BADGERprovides online applications to theuser, that is, procedures by which auser can overlay and manipulatelayers of geospatial data to generatean information product—fundamen-tal, online, geographic informationsystem functions.

Project personnel contributed toBADGER by development andimplementation of the BADGER/Internet home page interface;development of secure, robusttransaction protocols that allowBADGER users to access data onpublic and private servers; develop-ment of software for interactivelocation of parcels using streetaddresses or assessors’ parcelnumbers; and development andimplementation of specific BADGERapplications.

Two applications were demon-strated in FY96. The “Notice ofIntent” application, developed forthe Santa Clara Valley WaterDistrict, allows the owner/operatorof a commercial enterprise tocomply with a section of the cleanwater act by filing informationelectronically about the nature anddestination of runoff from the site.The application completes a formand supplies three images showingthe location as outlined on a digitalorthophoto quad (aerial photograph)and map sheet, and an imageshowing the classification of the

surface area of the site as pervious orimpervious. The application alsocalculates the percentage of land ineach category. The online applica-tion, designed by BADGER andoperated by BASIC, is expected toincrease compliance and lower costsfor the public and the agencyadministering the law. The secondapplication developed by Ames staffallows users to locate a parcel in theBay Area and display it in relation tocategories of known natural hazards,for example, flood, ground motionduring earthquakes, and wildfire.

BADGER is one way in whichNASA data and computationaltechnology are being used to servecommerce and real user needs, andto demonstrate the utility andpracticality of the Internet.

Point of Contact: E. Sheffner(650) [email protected]

Brazil/United StatesEnvironmental Monitoringand Global ChangeProgramJames Brass, Vincent Ambrosia

This program involves amultidisciplinary team of interna-tional researchers performingcooperative studies to identify andmitigate the extent and environmen-tal effect of deforestation andburning within the dry and wettropical forests of Brazil. Thisresearch is performed in collabora-tion with Philip Riggan of the U.S.Forest Service; Joao Pereira, HeliosaMiranda, and Antonio Miranda of

the University of Brazilia; TheresaCampos of the National Center forAtmospheric Research; RobertHiggins of SIMCO Electronics; andEdward Hildum of Sverdrup Tech-nology. The research is supported byNASA, the U.S. Forest Service, theU.S. Aid for International Develop-ment, the Instituto Brasiliero de MeioAmbient e dos Recusos NaturaisRenovaveis, the Brazilian NationalSpace Institute, the Universities ofBrazilia and Sao Paulo, and theNational Center for AtmosphericResearch.

Since 1992, aircraft campaignshave focused on the savannas of thecentral portion of Brazil. Collectingremote sensing and trace gasmeasurements, the campaigns havedocumented greenhouse gas genera-tion, nutrient movement, and cloudcondensation nuclei development infires throughout the central Braziliangrasslands. The fire data continue todocument the variability in flamingand smoldering conditions withinthe cerrados, with rates of spreadbetween 0.1 and 3.0 meters persecond and smoldering conditionslasting from 15 minutes to over3␣ hours. Consistency in emissionfactors for nitrogen and carbonspecies continues, depending on thefuel type and condition.

The FY96 campaign focused ondeforestation for the first time. Datafrom flights of the Airborne InfraredDisaster Assessment System over theAmazon basin and dry tropical forestdocumented large areas of cutting,similar to that of the Pacific North-west of the United States. The sensorsystem was able to discriminatebetween the two major types ofcutting (clearcuts and selective


149E C O S Y S T E M S C I E N C E A N D T E C H N O L O G Y

harvesting), where individual high-value species are removed from thesite.

Although the deforestation isimportant from many standpoints,the missions during August andSeptember of 1996 concentrated onthe impact of harvesting on fireoccurrence and behavior. Two typesof burning occur after harvesting oftimber. If the area is clearcut, theresulting fire is intense and leaves avisible fire scar that can be observedusing remote sensing. If the area isselectively harvested, fires occurringafter the cutting are less intense andleave no telltale sign of a fire scarbecause the overstory left behindobscures the scar evidence.

The FY96 campaign providedthe data necessary to determine therelationship between harvesting, fireactivity, and greenhouse gas genera-tion. These remotely sensed data arebeing analyzed and will helpquantify the amount of harvestingthat is occurring in each ecosystemand the resultant fire emissions. Thisinformation will be used to supportthe ongoing effort in Brazil toinventory the amount of greenhousegases being produced by biomasscombustion.

Point of Contact: J. Brass(650) [email protected]

Carnegie/Ames/StanfordApproach ModelChristopher Potter

The Carnegie/Ames/StanfordApproach (CASA) model wasdeveloped for the study of contem-

porary patterns and processes ofecosystem trace gas exchangebetween the terrestrial biosphere andthe atmosphere. The CASA model isunique in that it now simulates ahost of trace gas fluxes (carbondioxide (CO2), methane (CH4),carbon monoxide (CO), nitrousoxide (N2O), and nitric oxide (NO))on a scale that merges remotesensing, climate, radiation, vegeta-tion, and soils datasets with nutrienttransformation processes at the levelof the soil microsite. This researchwas performed in collaboration withPamela Matson of the University ofCalifornia, Berkeley, Peter Vitousekof Stanford University, and Eric A.Davidson of the Woods HoleResearch Center, Massachusetts.

The model has been refinedover the past year to run on either adaily or a monthly time interval tosimulate seasonal patterns in carbonfixation, nutrient allocation, litterfall,soil nitrogen mineralization, CO2,CO, N2O, NO emission, and CH4and CO uptake in soils. In FY96, anew global application of the CASAmodel, the hypothesis that variabilityin the ratio of N2O:NO emissionsover broad spatial gradients dependsupon seasonal patterns of soilwetting and drying, was examined. Itappears that gross rates of nitrogenmineralization account for majordifferences in gas emissions amongecosystem types. This finding hasadvanced the state of nitrogen (N)trace gas modeling notably bycalculating indices of the globaldistribution of N cycling processesand estimating trace gas emissionsbased directly on those quantifiedmineralization fluxes.

The latest version of the CASAmodel predicts a total emission flux

of about 6 teragrams (1012 grams) ofN-N2O per year and 10 teragrams ofN-NO per year from soils worldwide(as illustrated in the figure (see ColorPlate 21 in the Appendix)), exclusiveof N fertilizer sources. While tropicalforest ecosystems contribute over50% of global annual N2O emis-sions, cultivated areas are potentiallysignificant sources on a regionalbasis. The next research goal thatbuilds on the CASA foundation is todiscern the manner by which torepresent and apply fertilized soilsand associated trace gas emissions.

Point of Contact: C. Potter(650) [email protected]

Digital Array ScanningInterferometerSteve Dunagan, Philip Hammer

A scanning interferometer, thedigital array scanning interferometer(DASI), has been designed andfabricated for use in remote sensingof the ecosystem. The interferometeris based on charged-coupled-devicesensor technology, providingspectral sensitivity over the rangefrom 0.4 to 1.0 micron. Light fromthe ground scene is focused bymeans of an objective lens to anentrance slit aperture orientednormal to the scanning (flight)direction. After passing through theslit aperture, the light is collimatedand divided using polarization opticsinto equal amplitude polarizationvectors oriented along the ordinaryand extraordinary axes of a

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Wollaston prism. The two polariza-tion vectors are then recombined,collimated, and focused to the arraydetector, where an interferogram isformed. Ordinary and extraordinaryrays experience a path lengthvariation across the prism aperture.At the zero path difference location,the rays interfere constructively,regardless of wavelength, giving riseto a central peak intensity. On eitherside of this center burst wavelength,dependent interference gives rise to

an interferogram identical to theoutput of a scanning Michelsoninterferometer. The interferogramdimension (columns) of the arraymay then be Fourier transformed toyield the spectra of light originatingfrom a ground pixel defined by theprojection of the slit width and thearray column width. Rows of thearray provide the spatial distributionof information along the slit. Scan-ning the slit in the flight directionsweeps out an image hypercube.

The detector array, consisting of240 by 750 pixels, may be config-ured along with the optics in severaldifferent ways to optimize spectralbandwidth and emphasize eitherspectral or spatial resolution. Thearray output is digitized at 10 bits.The primary design configurationprovides a spectral range from 0.5 to1.0 micron, with theoretical spatialresolution of 4.3 meters in the flightdirection and 2.5 meters cross track


Hawaiian Pathfinder DASI Instrument Block Diagram

Galvonometer

DASIsensorcamers

DASI optics

Slitadjustment

RS-433

+5, ±12v

+5, +12v

+12v

+5v

+24v+24v+5, ±12v

RS-170

+5v±15v

+15v

window BNC videoconnector

41 pin 20 gage connector

RS-232

RS-170

9600 baudmodem

FOGgyro

Pitchcorrection

systemScenevideo

camera

Video switch

fast wideSCSI

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DC to DC power converters: ±15, ±12, 5VDC

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Hard disk

Canister P,T sensors

Cooling fans

Thermostatswitches

100 to 24 VDCpower converterPlatform

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Telemetrytranceiver

Telemetryreceiver

Videoreceiver

Time & GPS stamp

Videotransmitter

100 VDC mainpower bus

Groundoperatorterminal

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PCI/ISA passive back plane

parallel

pressure canister to maintain 1 atm forconvective coding of electronics SCSI

Fig. 1. Hawaiian Pathfinder DASI instrument block diagram.


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(at a 50,000-foot altitude), andtheoretical spectral resolution of13␣ nanometers at 0.5 micron and50␣ nanometers at 1.0 micron. (Notethat the interferometer samples atequal intervals in wavenumberspace, resulting in a variation ofwavelength resolution that scalesapproximately with lambda2).

The instrument has beeninterfaced to a data acquisitionsystem and packaged in a pressur-ized container for deployment on ahigh-altitude, remotely pilotedaircraft. The self-contained systemrequires less than 150 watts ofpower and weighs less than 10␣ kilo-grams. The data acquisition systemcomprises an industrial board levelcomputer, with an Intel Pentium100-megahertz processor, protocolcontrol information (PCI) bus, and256 megabytes of system random-access memory for direct memoryaccess storage of hypercube data. Adigital framegrabber and a smallcomputer serial interface (SCSI) diskcontroller interface to the maincomputer board through a PCIpassive backplane. An onboard4.3-gigabyte hard disk permitsstorage of up to 16 hypercubedatasets per flight. Data transfer islimited by the continuous streamingwrite speed of the hard disk, permit-ting the acquisition of 5 to 10␣ inter-ferogram frames per second. Aschematic diagram of the device isshown in the figure.

Point of Contact: S. Dunagan(650) [email protected]

Effect of Landuse onRegional Estimates ofConiferous Forest Waterand Carbon BudgetsJoseph Coughlan, Jennifer Dungan

Geographic information systems(GISs) and ecosystem models arecommon tools that “scale up”measurements from ecological fieldexperiments across landscapes,continents, and even the entireglobe. Many predictions about thecauses and effects of global changeon the environment employ thisscaling method in combination withremotely sensed data. NASA’s fieldexperiments in grasslands (the FirstInternational Satellite Land SurfaceClimatology Project Field Experi-ment) and in northern forests (theBoreal Ecosystem AtmosphericStudy) are two examples of the needto match the scale of ecological fieldmeasurements with remote-sensingdata.

Remote-sensing data often comefrom coarse resolution (approxi-mately 1 kilometer, or 0.63 mile)remote-sensing instruments such asthe National Oceanic and Atmo-spheric Administration’s (NOAA’s)advanced very-high-resolutionradiometer (AVHRR) and, in thefuture, NASA’s Earth ObservingSystem. The mismatch between thesize of the plots used in a fieldexperiment and the size of thelandscape units generated with thisrelatively coarse resolution data cancause scaling errors and result in anoverprediction of carbon and watercycling rates. Researchers in thisproject are quantifying this unit-sizeerror in a set of scaling experiments.

When moving from the plot scale(30 square meters) to climate modelscale (1-degree cells), errors of up to25 to 30% in regional water use andcarbon cycling are observed forconiferous forests in the westernUnited States.

Additionally, there is usually amismatch between the size andshape of the units representing thelandscape data used to make theregional estimates, but manyresearchers are unfamiliar with thiserror source. Project researchershave begun to document this GISerror and its effect on landscape-scale predictions made with ecosys-tem models. The two most commondata layers are remotely sensedvegetation represented as a digitalimage of 1-kilometer-(0.63-mile-)long cells and large polygonsmapping soil types that the GIStranslates into a digital format. Unitsize issues have important implica-tions consequences for the use ofsoils data because soil map unitsusually comprise spatial units muchlarger in size than the vegetationmap units.

In FY96, a new method wasdeveloped to control resizing of soilsand vegetation units used to predictplant photosynthesis. This methodreconstructs the soils data so thatthey are represented with “support”similar to the remotely sensedvegetation, the 1-kilometer(0.63-mile) grid cell. This reconstruc-tion method enables researchers toconduct controlled experimentswith GIS data at several spatialresolutions.

The method was implementedwith a federally sponsored soilsdatabase for the state of Oregon and


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a NOAA AVHRR image. The figure(see Color Plate 22 in the Appendix)shows two maps of soil waterholding capacity (SWHC) for aportion of the state. The top mapshows the homogeneous polygonscommonly used to spatially repre-sent soil variables. The bottom mapshows the result of the new methodfor SWHC. Using this new mapresulted in an underestimation biasof 11% in plant photosynthesisestimates for Oregon. The fact thatresults can vary significantly usingthe same model and data raisesserious issues for understandingregional and global effects of climatechange.

Point of Contact: J. Coughlan(650) [email protected]

Landsat ProgramEdwin Sheffner

The Landsat Program is thelongest running program to collectand distribute satellite imagery ofEarth. The first Landsat satellite waslaunched in 1972, and the next inthe series, Landsat 7, is scheduledfor launch in 1998. In the quartercentury of operation, the instrumentson Landsat have transmitted millionsof Earth images that have beenemployed by a broad user commu-nity for studies of global change,resource monitoring and assessment,local and regional planning, diseasecontrol, and education.

The primary program supporttask at Ames Research Center is toget information on Landsat to allelements of the Landsat data user

community, and to act as a reposi-tory for comments from the commu-nity on the current and futureoperation of the program. The task isaccomplished through the use of aLandsat Program home page on theInternet. The home page wasinitiated in FY95; in FY96, extensiverevisions and additions were made.Updated regularly with news itemsabout the program, the page con-tains links to similar pages in theUnited States and abroad. Approxi-mately half the users who log on tothe home page are from outside theUnited States. An online question-naire was also added in 1996 thatwill allow users to provide specificinformation on the programelectronically.

Point of Contact: E. Sheffner(650) [email protected]

Leaf ModelingLee F. Johnson, Chris Hlavka,Philip D. Hammer, David L. Peterson

The proper interpretation of aland surface reflectance detected byair- or satellite-borne remote-sensinginstrumentation generally requirescorrections for distortions caused bythe intervening atmosphere. If thesignal originates from a vegetatedsurface, corrections for canopy andleaf anatomical structure are alsoneeded. Although considerableprogress has been made in thedevelopment of models to isolatethe influence of atmosphere andcanopy, less effort has been given todistortion due to leaf structure.

To address this factor, a within-leaf radiative transfer model (LeafExperimental Absorptivity FeasibilityModel, or LEAFMOD) has beendeveloped and tested againstempirical data. The model simulatesthe photon scattering and absorbingprocesses within the leaf, basedupon solution of the one-dimensional radiative transferequation, assuming a slab of leafmaterial with homogeneous opticalproperties. When run in the forwardmode, LEAFMOD generates the leafbidirectional reflectance and trans-mittance profiles given a specifiedleaf thickness, optical characteristics(scattering and absorption profiles) ofleaf constituents, and concentrationsof leaf constituents. In the inversemode, LEAFMOD computes the totalwithin-leaf absorption and scatteringcoefficients from the measured leafthickness, reflectance, and transmit-tance. Inversion experiments withreal and simulated data demon-strated that the model appropriatelydecouples scattering and absorptionprocesses within the leaf.

The model produced absorptionprofiles for fresh leaves, with peaksat locations corresponding to themajor absorption features of waterand chlorophyll. Using availablespectral data for grape leaves, themagnitude of the absorption coeffi-cient profile in the visible region wasstrongly correlated to chlorophyllconcentration determined fromconventional laboratory analysis.Spectral data from a leaf-stackingand drying experiment demonstratedthat absorption features related tovarious biochemical constituentscould be identified in the dry-leafabsorption profile derived byLEAFMOD.



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The model can be used toevaluate fresh-leaf spectral sensitivityto leaf chemistry, and also toinvestigate the influence of bothleaf chemistry and leaf amount onvegetation canopy reflectance. BarryGanapol, University of Arizona,collaborated with the Ames investi-gators on this project.

Point of Contact: L. Johnson(650) [email protected]

Mapping NorthernEcosystems: Applicationsfor Circumpolar MethaneExchangeVern Vanderbilt, Guillaume Perry,Joel Stearn

The goals of this project are toimprove estimates of the areal extentof northern, high-latitude wetlandsand to gain insight into the role ofnorthern ecosystems in the globalmethane (CH4) budget and, in sodoing, provide improved estimatesof global CH4 exchange.

The role of northern wetlandsin global atmosphere/biosphereinteractions remains an unresolvedbut key factor in projecting climaticchange in response to increasingatmospheric concentrations ofgreenhouse gases, such as carbondioxide and methane. Wetlandsnorth of 45°N represent globallysignificant methane sources—theorganic carbon stored in the peatand soil beneath these ecosystemsexceeds that of any other biome onEarth. Since climatic warming ispredicted to be most dramatic in

northern high latitudes, microbialdecomposition processes acting onthese carbon stores will almostcertainly lead to increased atmo-spheric loading of carbon dioxide(CO2) and CH4, thus potentiallyenhancing the greenhouse phenom-enon even further.

The areal representation ofboreal wetlands, the source areas forCH4, is poorly known on regional toglobal scales, particularly the arealextent of bogs, fens, and open-waterlakes and ponds. Various estimatesof the areal extent of northernwetlands differ nearly sevenfold.These differences in global invento-ries lead to large discrepancies in theestimation of overall exchange ofCH4 from northern sources and sinksbecause emission rates from thevarious individual land covers (fens,bogs, open water, wetlands, andnonwetlands) can vary by a factor ofmore than 100:1.

The analysis of results for theBoreal Ecosystem-Atmosphere Study(BOREAS) shows that glitter, thesometimes visually blinding sparkleof sunlight from water surfaces,provides a powerful signal uniquelyidentifying inundated areas. TheseBOREAS results demonstrate thatinundated areas may easily beseparated from noninundated areas.It is also possible to discriminate andaccurately classify fens, open waterareas, and forested areas because thevisually blinding glitter of sunlightoff ruffled water surfaces provides astrongly angular signature reflectioncharacteristic of wetlands. Conse-quently, these classifications andestimates of the areal extent of fensand open water areas are signifi-cantly more accurate than similarestimates based upon other sources

of remotely sensed data, such as theLandsat thematic mapper (TM)sensor. These encouraging resultsprovide an order of magnitudeimprovement in the accuracy ofestimates of the areal extent ofwetlands in the BOREAS studyregion.

Point of Contact: V. Vanderbilt(650) [email protected]

Modern EcosystemsResearch: Effects ofIncreased UV-B RadiationHector L. D’Antoni, J. W. Skiles

The link among these efforts isthe process of stratospheric ozonedepletion and the consequentincrease of ultraviolet-B radiation(UV-B) in the biosphere. Given thedeleterious effect of excessive UV-Bin living organisms, it is imperativeto establish what effects, if any, areproduced by the current levels ofUV-B.

Using alfalfa (Medicago sativaL.) as the experimental plant, severalhypotheses have been tested,including: (1) production of screen-ing pigments is stimulated by UV-Bradiation; (2) node elongation isaffected by UV-B radiation; (3)␣ phe-nological stages (that is, flowering)are controlled by UV-B radiation;and (4) alfalfa plants grown underUV-B exclusion have higher chloro-phyll concentration. In contrast withmost of the work published in thisarea of research, these experimentswere carried out with sunlight as theonly source of UV-B radiation.


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Plants that were grown in a growthchamber in June were transferred toa shed in the field and grown therefor 6 to 8 weeks. The shed providedtwo chambers with identical envi-ronmental conditions except for theUV regime. Chamber 1 is fitted witha cellulose acetate screen thatremoves 15% of the UV bandirradiance to simulate a preozone-depletion environment. Chamber 2is fitted with a polyester screen thatremoves the entire UV-B irradianceband. The experiments, run the pasttwo summers, have validated all fourhypotheses and led to new questionsand hypotheses. Data requireintensive statistical analysis beforepublication.

A similar effort with the Univer-sity of Mar del Plata in Argentina hasresulted in several outcomes. TheAntarctic spring-time “ozone hole”often reaches southern SouthAmerica during the austral spring.Data show that 15 to 18 days of thethree-month season have a lowstratospheric ozone concentration inUshuaia (southern Argentina), whileground-level UV-B records areconcomitantly high. Negativecorrelation was found betweenstratospheric ozone concentrationand UV-B irradiance at ground level.Negative correlation is higher inthe wavelength range of 289 to307␣ nanometers, known to damageDNA, chlorophyll, indole aceticacid, gibberelins, abscisic acid, andother important plant growthmolecules.

An extended visit to Argentinaresulted in the reflectance analysesand in daily measurements ofsolar irradiance in the 300- to750-nanometer range in Mar delPlata (38°S) that can be compared to

those of Moffett Field, at approxi-mately the same latitude in theNorthern Hemisphere.

This research was performed incollaboration with G. R. Daleo,S. Burry, M. C. Lombardo, A. C.Mayoral, P. Palacio, and M. E. Triviof the University of Mar del Plata,Argentina; Roy Armstrong, J.Corredor, and J. Morell of theUniversity of Puerto Rico(Mayaguez); and Jaime Matta of thePonce School of Medicine, Ponce,Puerto Rico.

Point of Contact: H. D’Antoni(650) [email protected]

Optimizing an EcosystemModel for Use on Parallel/Distributed ProcessorsJ. W. Skiles, Cathy Schulbach

The goal of this project is toupdate models/codes based oncurrent ecological knowledge withstate-of-the-art computer simulationtechnology. Such modifications willdecrease execution time, enablingsimulation of larger geographicalareas and/or performance of moresimulation experiments. Areas ofemphasis are in ecology and com-puter science, with the expectationthat techniques developed in thisproject will serve as a blueprint forthe construction of future Earthsystem models that will be run onsupercomputers showing howprocesses can be coded for distrib-uted processing. In addition, thisproject is expected to enhance AmesResearch Center’s expertise in the

areas of information technology andecosystem science.

As a demonstration, a grasslandecosystem model is being used tosimulate the Great Plains (GP) of theUnited States, an area of approxi-mately 60,000 advanced very-high-resolution radiometer pixels. Largeamounts of data are necessary toinitialize the model for operation ona geographical area of this size. Datarequired include soil types, plantcommunity information, andweather drivers. A major undertak-ing is the establishment of datastructures whereby the model canaccess correct information for aspecified location, access storedsoils data, calculate intermediateand state variables, and updatebiomass and soil-water variables ona pixel-by-pixel basis across the timeframe of the simulation. All this is tobe done while maintaining thebiological and ecological dynamicsof the ecosystem(s) being simulated.

Computer science areas ofemphasis are: (1) establishingprotocols for rehosting scalar codeto vector supercomputers anddistributed-processing super-computers; (2)␣ validating metricsfor load balancing and processorscheduling; (3) using different typesof ecological model codes (differ-ence equation, partial differentialequations, correlation equation) inthe distributed environment; and(4)␣ using automated tools to aid inthe rehosting process.

Although most ecosystemmodels include state-of-the-artecological concepts, they employscalar coding that does not takeadvantage of the power of contem-porary computing platforms.



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Rehosting these codes to super-computers entails restructuring thecode itself and using availablecommand-level instructions duringcompilation.

Because of weather patterns andthe resultant plant communities onthe GP, it is possible that somelocations will have growing plantswhile others will not. This scenariosometimes causes a processor on amultiprocessor supercomputer to beidle while others are processing theplant growth part of the code.Activity in this project focuses onefficiently balancing the load of eachprocessor so that none are idle,thereby decreasing the executiontime for the simulation experiment.

Progress to date includes theconstruction of interpolation algo-rithms for missing data, stochasticweather generation for 31 locationson the GP, and the establishment ofgaming scenarios for global changemodeling, including the incorpora-tion of increases or decreases intemperatures and precipitation andthe seasonal timing of precipitationevents.

Point of Contact: J. Skiles(650) [email protected]

PaleoenvironmentalResearchHector L. D’Antoni

The goal of this research is tocalibrate modern pollen data interms of satellite remote-sensing dataof modern vegetation, producecalibrated equations of pollen as a

function of vegetation, and use theseequations to “hindcast” (as opposedto forecast) past vegetation fromfossil pollen sequences obtainedfrom stratified sediment deposits.

Many models used to predict theenvironmental future of Earth aredriven by remotely sensed data ofvegetation. Historical remote-sensingdatabases of vegetation reach backonly a few decades. Such a timeframe is not sufficient to appreciatelong-term environmental processes.Paleoenvironmental data might helpsolve this problem. However,paleoenvironmental data are notcompatible with remotely senseddata and, hence, they are of limiteduse for modeling.

The efforts in FY96 concentratedon the Oregon Pollen Transect, acollection of modern pollen samplesfrom central Oregon, taken every10␣ miles from Dayville in centralOregon to Newport on the Pacificcoast, and crossing vegetation zonesof ponderosa pine, western juniper,fir and Douglas fir, western hemlock,alder, and sitka spruce. A predictiveequation of remote-sensing vegeta-tion indices such as the normalizeddifference vegetation index (NDVI)was completed. Vegetation inOregon has changed during the last50 years, and in some localities theoriginal floristic composition isdifficult to determine from currentevidence. To solve this problem, adatabase has been constructed withmodern pollen data producedbetween 1930 and 1949. These datawill help to recalibrate predictiveequations of NDVI and other indicesand, in turn, these equations willassist to hindcast Holocene (that is,the last 10,000 years) vegetation


indices that can be used in predic-tive models of environmentalchange. Thus, the data used toparameterize these models will spanover 10,000 years rather than thecustomary few decades and willhelp differentiate long cycle fluctua-tions from meaningful trends ofenvironmental change.

Point of Contact: H. D’Antoni(650) [email protected]

Scientists’ IntelligentGraphical ModelingAssistantJennifer Dungan

Over the past 30 years, scientificsoftware models have played anincreasingly prominent role in theconduct of science. Unfortunately,implementation of scientific modelscan be difficult and time-consuming,and software engineering supportavailable specifically for construct-ing scientific models is scant.Scientists’ Intelligent GraphicalModeling Assistant (SIGMA), aninteractive, knowledge-based,graphical software developmentenvironment, was created at Ames tofill this gap. SIGMA is designed tohelp scientists rapidly prototype theirscientific models by simplifyingconstruction, modification, andreuse of modeling software, and toprovide a supportive computationalenvironment for exploratory modelbuilding.

In FY96, two well-knownmodels describing radiative transferin vegetation canopies were added

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to the SIGMA knowledge base.Sensitivity experiments were con-ducted with these models to investi-gate the relative importance ofmodel variables in a more systematicway than is usual with traditionalprogramming languages. In addition,two graduate students at separateuniversities tested SIGMA over theInternet. They were able to navigatethe data flow graph for the ecosys-tem model, query the knowledgebase for details on variables andequations, and build the rudimentsof a new model.

Point of Contact: J. Dungan(650) [email protected]

Atmospheric Chemistry

Airborne NaturalRadionuclideMeasurements in theDevelopment andValidation of GlobalThree-DimensionalModelsMark Kritz, Stefan Rosner,Robert Chatfield, Leonard Pfister

As the sources, lifetimes, andatmospheric behavior of naturalradionuclides (for example, 7Be, 32P,210Pb, and 222Rn (radon)) aregenerally well understood, compari-son of their observed distributionswith model prediction is findingincreasing application in the devel-opment and validation of the globalmodels used to assess global change.Such comparisons, the focus of two


international workshops (December1993 and August 1995) sponsoredby the World Climate ResearchProgramme, are a key element in thevalidation of the models to be usedto assess the possible impact ofaircraft emissions on the atmospherein NASA’s Atmospheric Effects ofAviation Program (AEAP).

Project activity in this area hasbeen divided between the acquisi-tion and the application of airborneradionuclide measurements for thispurpose. Over the last decade, theinstrumentation has flown on morethan 100 flights aboard NASAaircraft, including the C-130, C-141,DC-8, and ER-2. For example, in thesummer of 1994, the instrumentationwas onboard the C-141 on 15 flightsout of Moffett Field, acquiring astatistically significant climatology ofthe summertime vertical distributionof radon over northern California.This dataset found extensive applica-tion at the August 1995 WorldClimate Research Programme(WCRP) Workshop, and is currentlybeing used in the validation of theNASA AEAP core model.

A more extensive set of similarairborne radon measurements wasobtained over the central andwestern United States in the summerof 1996, flying aboard a NASA Learjet. In addition to radon, measure-ments of carbon monoxide (CO),carbon dioxide (CO2), and methane(CH4) were made in cooperationwith the National Oceanic andAtmospheric Administration (NOAA)Climate Monitoring DiagnosticsLaboratory, Boulder, Colorado, andmeasurements of ozone (O3) weremade in cooperation with theNational Center for AtmosphericResearch Facility, Boulder, Colo-

rado. The combined dataset will beused by NOAA in refining theirbudgets of these carbon species inthe northern hemisphere, and in thedevelopment and validation of atleast two three-dimensional globalchemical transport models.

Point of Contact: M. Kritz(650) [email protected]

Reactive NitrogenData from the UpperTroposphere and LowerStratosphereHanwant B. Singh, Alakh Thakur,Peter Mariani

NASA has launched a subsonicaircraft assessment program (SASS)to determine the effect of the currentand future subsonic fleet on theEarth’s environment as quantitativelyas possible. A key SASS objective isto assess the effect of nitric oxide(NO) emissions from subsonicaircraft on atmospheric ozone (O3),especially in the region of the uppertroposphere/lower stratosphere. Alarge number of airborne studies inthe free troposphere (for example,global troposphere experiment (GTE)and tropospheric ozone/stratosphericozone (TROPOZ/STRATOZ)) andlower stratosphere (for example, theAirborne Arctic StratosphericExpedition II) have been performedin the last decade, and a sizablebody of data on reactive nitrogenspecies has been collected from bothhemispheres. Although these datahave been, to a degree, analyzed asindividual datasets, no comprehen-

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sive analysis and synthesis has beenundertaken. Tasks in this study are toacquire, analyze, and interpretexperimental data on reactivenitrogen species (along with ozone,hydrocarbons, and selected tracers)that have been collected over thelast decade, with focus on the uppertroposphere and lower stratosphere.The aim is to provide an overallsynthesis of the present understand-ing of reactive nitrogen chemistryand recommendations for futurefield research, based on a compre-hensive analysis of available data.Analysis of these data was com-pleted in FY96 and the results arebeing finalized.

Point of Contact: H. Singh(650) [email protected]

Airborne AutotrackingSunphotometryPhilip B. Russell, John M. Livingston,James Hanratty, Damon Ried,Jill Bauman

Atmospheric aerosols (suspen-sions of airborne particles compris-ing hazes, smokes, and thin cloudsin the troposphere and stratosphere)play important roles in determiningregional and global climates, thechemical composition of the atmo-sphere, and atmospheric transportprocesses. As knowledge hasadvanced in each of these fields, sohas recognition of the importance ofaerosols. As a result, national andinternational bodies have called forincreased efforts to measure aerosolproperties and effects, as a means of

improving predictions of futureclimate, including greenhousewarming, ozone depletion, andradiation exposure of humans andother organisms.

A fundamental measure of anyaerosol is the way it attenuates abeam of light of various colors (thatis, wavelengths). This attenuation isusually described in terms of thequantity optical depth. The depen-dence of optical depth on lightwavelength is the optical depthspectrum.

The Ames airbornesunphotometers determine theoptical depth spectrum of aerosolsand thin clouds by tracking the sunand measuring the (relative) intensityof the solar beam in several spectralchannels. The tracking head of eachinstrument mounts external to theaircraft cabin, so as to increase data-gathering opportunities relative toin-cabin sunphotometers and also toavoid data contamination by cabin-window effects. Each channelconsists of a baffled entrance tube,an interference filter, a photodiodedetector, and an integral preampli-fier. The filter/detector/preamplifiersets are temperature-controlled toavoid thermally induced calibrationchanges. Each instrument includesan entrance-window defoggingsystem to prevent condensation (aproblem otherwise common inaircraft descents). Solar tracking isachieved by azimuth and elevationmotors driven by differential sunsensors. In general, sun tracking isachieved continuously, independentof aircraft pitch, roll, and yaw,provided rates do not exceedapproximately 8 degrees per secondand the sun is above the aircraft

horizon and unblocked by clouds oraircraft obstructions (for example,tail, antennas).

Data are digitized and recordedby an onboard data acquisition andcontrol system. Real-time dataprocessing and color display areroutinely provided. The sciencedataset includes the detector signals,derived optical depths, detectortemperature, sun tracker azimuthand elevation angles, tracking errors,and time. Each instrument mustmaintain its radiometric calibration(including window and filter trans-mittance, as well as detectorresponsivity and electronic gain) towithin 1% in each spectral channelfor periods of several months to ayear.

In July 1996, the first scienceflights of the 14-channel sun-photometer (developed under theNASA Environmental ResearchAircraft and Sensor TechnologyProgram) were made on the Pelican(modified Cessna) aircraft of theCenter for Interdisciplinary RemotelyPiloted Aircraft Studies during theTropospheric Aerosol RadiativeForcing Observational Experiment.

Point of Contact: P. Russell(650) [email protected]

Analysis of Stratosphere/Troposphere ExchangeLeonhard Pfister, Henry Selkirk

Aircraft atmospheric samplingexperiments require the support andadvice of meteorologists to besuccessful. The purpose of this

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project is to analyze meteorologicalfields both during and after fieldexperiments so as to maximize thescientific return of the samplingcampaigns. The emphasis in thisproject is to provide meteorologicalsatellite information as it pertainsto stratospheric transport andstratosphere/troposphere exchangeprocesses.

During FY96, Ames providedmeteorological coordination for theStratospheric Tracers of AtmosphericTransport (STRAT) ER-2 samplingmission and the Tropical OzoneTransport Experiment (DC-8 mis-sion). Three major STRAT fieldcampaigns were undertaken. Backtrajectory analyses of STRAT datayielded evidence that midlatitudecirrus shields can determine thewater vapor content of the lower-most stratosphere. Some simplecloud height algorithms that can beused in real time for flight planningfor the low-altitude (tropospheric)ER-2 flights have been developed.These algorithms use a combinationof meteorological analyses andsatellite imagery to determine thecloud altitude at any point in asatellite image.

Finally, it has been shown thatthe subvisible cirrus observed by theDC-8 south of Hawaii are probablydue to air that originates inMicronesia and travels northward tothe subtropical jet, eastward towardHawaii, and southward—followingan upper tropospheric/lower strato-spheric anticyclone.

Point of Contact: L. Pfister(650) [email protected]

Use of Argus inAtmospheric StudiesMax Loewenstein

The Argus instrument, a tunable-laser, infrared spectrometer, wasdesigned to measure the long-livedtracers methane (CH4) and nitrousoxide (N2O) in the stratosphere up toaltitudes of 30 kilometers. The ratioof these two tracers as a function ofaltitude provides important informa-tion on the dynamics of differentregions of the stratosphere: the surfzone, the tropical pipe region, andthe polar region distinguished by itsstrong winter vortex isolation.

In June and September 1996, thenew Argus lightweight N2O andCH4 instrument was completed andflown on balloon launches to higherthan 30 kilometers from Ft. Sumner,New Mexico (34 degrees N), the siteof the NASA National ScientificBalloon Facility. In June, the instru-ment performed flawlessly in anengineering sense, but no reportabledata resulted because of inadequatecontrol of the diode laser mounttemperatures. This control limitationwas corrected in time for the Sep-tember launch. In September, allaspects of the Argus instrumentperformed well, and ascent anddescent profiles for N2O wereobtained. The methane channel isbeing brought up to operationalstatus.The Argus instrument has beenprepared and shipped to Juazeiro doNorte, Brazil, for use in the OrbiterManeuvering System tropical fieldcampaign.

Point of Contact: M. Loewenstein(650) [email protected]

Airborne Tunable LaserAbsorption SpectrometerMax Loewenstein, James R. Podolske

The Airborne Tunable LaserAbsorption Spectrometer (ATLAS)instrument was designed and built inthe mid-1980s to measure strato-spheric tracer fields from the ER-2high-altitude research aircraft.During the decade of its operation,ATLAS has been used primarily tomeasure the nitrous oxide (N2O)tracer field on several campaignsprimarily focused on polar andmidlatitude processes in the strato-sphere. N2O is a very long-livedtracer of stratospheric dynamics.Normally, chaotic-appearingobservations of molecular constitu-ents of the atmosphere such asreactive nitrogen (NOy), carbondioxide (CO2), water vapor (H2O),chloro-fluoro-carbons (CFC) andothers are “smoothed” by construct-ing correlation diagrams of theseobservations plotted versus N2O.These correlations then provideimportant chemical and dynamicaldiagnostic information on the stateof the atmosphere.

The ATLAS instrument took partin the continuing StratosphericTracers of Atmospheric Transport(STRAT) campaigns, with fielddeployments carried out in October1995 and February, July, andSeptember 1996. The instrumentcontinues to work flawlessly andreturns very-high-quality N2O tracerdata on all flights. ATLAS N2O datacontinue to be the dataset of choicefor analyses carried out within theSTRAT community. Data compari-sons with the aircraft laser infrared



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absorption spectrometer (ALIAS) andairborne chromatograph atmo-spheric trace species (ACATS) N2Opresented at a July 1996 STRATworkshop show that ATLAS data areof the highest quality and are true toits stated 3% accuracy.

During the Airborne SouthernHemisphere Ozone Experiment andthe follow-on Stratospheric Tracersof Atmospheric Transport campaignin 1995 and 1996, a comprehensivenew dataset on CO2 and N2O in thenorthern hemisphere extending fromthe equator to 60 degrees N wasaccumulated. Several importantresults have emerged from this newand unique dataset: Tropospheric aircarrying its normal seasonal cycleand secular trend of CO2 continu-ously enters the lower tropicalstratosphere and is rapidly (in aboutone month) transported to bothhemispheres. The mean age of theobserved midstratospheric air isabout 6 years. Pollutant exhaustgases, which will be deposited byproposed new stratospheric aircraftinto the midlatitude lower strato-sphere, will probably exceed thebest current predictions by 30 to100%. These results may haveimportant implications for theinfluence of stratospheric aircraft onthe ozone layer.

Point of Contact: M. Loewenstein(650) [email protected]

Convectively GeneratedGravity WavesLeonhard Pfister

This work evaluates the influ-ence of gravity waves generated byconvection on stratospheric circula-tion in the tropics. Each convectiveevent emits a spectrum of gravitywaves with a broad variation ofphase speeds. These waves willbreak at a variety of altitudescorresponding to these phasespeeds; when they do, they willexert a force at that altitude that canaffect the overall circulation of thetropical stratosphere. Understandingthe nature of this force quantitativelyis essential to obtaining a compre-hensive picture of the transport oftrace constituents such as ozone, aswell as the constituents that governozone production and destruction.The assessment of the importance ofthese convectively generated gravitywaves has two steps: evaluation ofthe amplitude and spectrum ofwaves from each convective systemusing measurements, and extrapola-tion of these results to global budgetsusing global satellite information.

This task has progressed in twoareas. First, half-hourly datasets ofgeostationary operational environ-mental satellite (GOES-8) imageryfor the strongly convective Panamaregion have been prepared forspectral analysis. The objective is touse the satellite data to establish thefrequency distribution at shorterspatial and time scales than thataddressed by previous satellitespectral studies. Second, two casestudies of gravity waves generatedby convection as observed by ER-2aircraft measurements have been

completed. One of these, from theStratospheric Tracers of AtmosphericTransport campaign, shows gravitywaves with horizontal wavelengthsof about 50 kilometers and verticalwavelengths of 5 to 10 kilometers.This result suggests that a simple“transient mountain at the tropo-pause” conceptual model canexplain only part of the mesoscalegravity wave variance. Evidence wasalso found of inertia-gravity waveswith horizontal wavelengths of1000␣ kilometers, consistent withstudies that inferred horizontalwavelengths using vertical profilesand inertia-gravity wave dispersionrelationships.

Point of Contact: L. Pfister(650) [email protected]

The ER-2 and DC-8MeteorologicalMeasurement SystemsK. Roland Chan, T. Paul Bui,Antonio A. Trias, Stuart W. Bowen,Jonathan Dean-Day

The Meteorological Measure-ment System (MMS) provides in situ,high-resolution meteorologicalparameters (pressure, temperature,and the three-dimensional windvector). The MMS consists of threemajor systems: (1) an air-motionsensing system to measure thevelocity of the air with respect tothe aircraft; (2) an aircraft-motionsensing system to measure thevelocity of the aircraft with respectto the Earth; and (3) a data acquisi-tion system to sample, process, and


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record the measured quantities.Since much of the instrumentation isattached to the aircraft at speciallychosen locations, the MMS is aplatform-specific instrument thatcannot be transported from oneaircraft to another.

The MMS is uniquely qualifiedto investigate atmospheric mesoscale(gravity waves) and microscale(turbulence) phenomena. Since theMMS provides quality data onatmospheric state variables, MMSdata have been extensively used inalmost all investigations to interpretthe in situ experiments aboard thesame aircraft.

Over the past decade, the ER-2MMS has successfully participated inmany missions, including theStratospheric Tracers AtmosphericTransport missions in FY95 andFY96.

The MMS instrumentation hasbeen modified several times. Recentsignificant modifications to improvethe system reliability include:(1)␣ improved navigation data usingthe Litton LN-100G, a lightweightring laser gyro embedded in theGlobal Positioning System inertialreference system; (2) improved staticpressure measurement accuracy andprecision by using quartz diaphragmtransducers, which have very lowthermal expansion coefficients;(3)␣ improved pitot pressure measure-ment, and hence true-air-speedmeasurement by customizing thepressure range calibration to theER-2 flight envelope; and (4) aRosemount open-wired, fast-temperature sensor installed forwardon the fuselage, well outside ofperturbed boundary layer flow,

making the temperature measure-ment independent of the aircraftattitude effects.

The DC-8 MMS is a newinstrument, flight-tested for the firsttime in May 1996. The MMSperformed very well during thesubsonic aircraft: contrail and cloudeffects special study, which alsobegan its deployment mission inMay. A preliminary set of MMSproducts are measurements of staticpressure (p), temperature (T), theeast/west component of wind (u,with east being positive), the north/south component of wind (v, withnorth being positive), the verticalcomponent of wind (w, with upbeing positive), latitude, longitude,and pressure altitude. Analysis of thethree sets of temperature data (twosets from the Tslow probe and one setfrom the Tfast probe) indicates thatthe self-consistency of the tempera-ture measurement is within±0.3 degree kelvin of the MMSdesign specifications.

Point of Contact: K. Chan(650) [email protected]

Environmental ResearchAircraft and SensorTechnologySteve Wegener

Environmental research aircraftand sensor technology (ERAST)provides focus for critical technologydevelopment and flight demonstra-tion that reduces the technical andeconomic risk of using remotelypiloted aircraft (RPA) as a means to

collect scientific data in a timely andcost-effective manner. The ERASTsensor element addresses the scienceand payload aspects of RPA mis-sions. Early focus centered oninstruments for high-altitude(25␣ kilometers) atmospheric re-search. More recently, efforts havesupported a wider range of sciencemission development activities,embracing a broader range of users.The present research is beingperformed in collaboration with theNational Oceanographic andAtmospheric Administration, otherNASA Centers, the National Centerfor Atmospheric Research, the U.S.Department of Energy Laboratories,several universities, and the Office ofNaval Research. New concepts inRPA over the horizon (OTH) com-munications, key to extendedmissions, are being developed andtested. Research in extremelyminiaturized sensor technologiesholds promise for profound changesin the capability of RPAs.

The ERAST sensor element madesignificant contributions to theoutreach in both the sensor andplatform communities in FY96. Thesensor element sponsored threeretreats for sensor engineers duringthe year, which brought together asmall group of experienced engi-neers from ERAST instrumentdevelopment projects.

The ERAST sensor elementdemonstrated a major milestone inFY96: the ability to monitor andcommand RPA payloads via asatellite communications link. Theairborne data system and an infraredcamera aboard the Scaled Compos-ites D2 RPA were monitored forstatus, the communication packagewas reconfigured in flight, and the



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camera was commanded to acquireimagery and downlink data. Thisaccomplishment demonstrates theability to monitor and commandplatforms and payloads OTH, acapability critical for operation atdistances greater than 160 kilome-ters from homebase. OTH communi-cations supporting interactiveresearch platforms will enhanceoperational safety and scientificproductivity.

The ERAST OTH communica-tion development effort provided thefollowing OTH hardware capabili-ties in FY96:␣ ␣ •␣ ␣ The telemetry interface and datasystem was upgraded to be compat-ible with the Tracking and DataRelay Satellite System (TDRSS)interface electronics. Flight testswere conducted in December 1995and September 1996.␣ ␣ •␣ ␣ TDRSS Interface electronics.␣ ␣ •␣ ␣ An infrared imaging payload wasdeveloped to demonstrate the OTHcapability, build expertise for remotesensing science, and foster coopera-tion with the Lawrence LivermoreNational Laboratory.␣ ␣ •␣ ␣ System integration and testingdemonstrated the system capabilityon NASA Lear jet and ERAST D2platforms.␣ ␣ •␣ ␣ A systematic approach torequesting and obtaining approvalfor use of radio frequency spectrafor TDRSS demonstration wasestablished.␣ ␣ •␣ ␣ A “roadmap” for OTH capabilityfor the ACE 2 was established.Extremely small sensor systems arekey to placing meaningful payloadsat very high altitudes. Newapproaches to sensor systems arebeing explored to reduce payload

weight, volume, and powerrequirements.

The ERAST sensor elementsponsored a review of currentatmospheric science instrumentsused in the Upper AtmosphereResearch Program. The intentionwas to identify approaches wheremicromachine concepts might leadto significant breakthroughs requiredto shrink, in a revolutionary way, theweight, volume, and power con-sumption of today’s payloads. Thestudy (in technical review) con-cluded that, although some reduc-tion was possible, reductions by afactor of ten required new measure-ment concepts. New work in surfaceacoustic wave technology suggeststhat sensitivities comparable totoday’s instruments can be achievedin shoe-box size packages. Incollaboration with NASA’s MarsPathfinder project, NASA’s Sensors2000!, Sandia National Laboratories,the University of California, Berke-ley, and the Jet Propulsion Labora-tory, the ERAST sensor element isfunding a laboratory study todemonstrate parts-per-billionmeasurement of carbon monoxide(CO), nitrous oxide (N2O), watervapor, and ozone with acoustic(surface acoustic wave and flexuralplate) and chemiresistive technolo-gies. Demonstration of these resultsin a modular sensor array instrumentis slated for FY97.

Point of Contact: S. Wegener(650) [email protected]

Global EmissionsInventories for Radonand the CosmogenicRadionuclidesMark Kritz

Natural radionuclide measure-ments are finding increasing applica-tion in the development andvalidation of global circulation andchemical tracer models. In particu-lar, comparisons of the atmosphericradon distributions predicted byglobal models with radon measure-ments made at a surface station andaboard NASA aircraft flying in thefree troposphere have been used intwo recent World Climate ResearchProgramme workshops, and by theGlobal Modeling Initiative compo-nent of NASA’s Atmospheric Effectsof Aviation Program, to identifyshortcomings in the convective andlong-range horizontal transportparameterizations used in state-of-the-art global atmospheric models.However, as this work has continuedand progressed and models havecontinued to improve, there hasbeen a growing need to review andperhaps reassess current estimates ofthe source functions for theseradionuclides, including not onlythat of radon (222Rn) but alsothose of 7Be and other naturalradionuclides.

To this end, the InternationalGlobal Atmospheric Chemistry(IGAC) Program has included anatural radionuclide element in itsGlobal Emission Inventories Activity(GEIA). The natural radionuclidepanel, functioning under the GEIA/IGAC umbrella, has participants


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from France, Germany, Japan, NewZealand, and the United States.Projects in FY96, performed incollaboration with Stephen Scheryof the New Mexico Institute ofTechnology and Phil Rasch of theNational Center for AtmosphericResearch, included: (1) work on aglobal radon emissions map toreplace the 1atom/centimeter2/second global mean value currentlyin widespread use, and (2) initiating(as a complement to direct onsitelocal point surface flux measure-ments) a subproject to infer theglobal mean radon source functionsusing long-term observed meanatmospheric distributions of radonand the deposition at the surface ofits decay product 210Pb.

Point of Contact: M. Kritz(650) [email protected]

The Great African Plume:Tropical Carbon Monoxideand Ozone SimulationRobert B. Chatfield

Maintenance of high concentra-tions of pollutants, for example,tropospheric carbon monoxide andozone, in seemingly distant regionsof the tropical troposphere is thefocus of this research. Each of thesecompounds has a major role incontrolling the oxidizing capacity ofthe lower atmosphere. It was thoughtthat the source of a particularlystriking accumulation of tropo-spheric ozone in the middle of theEquatorial Atlantic Ocean was dueto biomass burning taking place in

South America or Africa. However,until this work, the roles that eachplayed and the process for mid-oceanic, midtropospheric pollutionwere not clear. The work describesthe origin and character of theGreat African Plume from biomassburning.

A three-dimensional tropo-spheric chemistry model thatassimilates the winds and weatherthat prevailed during NASA’sairborne expedition, the TropicalAtmospheric Chemistry Experi-ment—Atlantic, has been created.The model also helps to establishimportant quantitative details, suchas the amount of biomass-burningemission of carbon monoxide andthe ability of clouds to vent materialto the upper troposphere. The latterventing process creates the UpperSouth American Plumes and theUpper African Plume, which pollutevirtually the entire southernhemisphere.

The maintenance of the concen-trations of carbon monoxide andtropospheric ozone are the results ofcomplex interplay of many naturaland social phenomena that make uptropical agriculture, followed byinteractions of many chemicalspecies and meteorological pro-cesses. This project has madeexplicit several, while pointing out aremaining anomaly in the theory thatis now widely recognized. The mostvisible concentration of troposphericozone in the mid-Atlantic appears tobe caused by the Great AfricanPlume, which extends up to about6␣ kilometers. This plume arises outof a convergence of polluted mate-rial in Equatorial and SouthernAfrica. Pollution is then lofted in theinteroceanic convergence of the

region, by processes that involveintense boundary layer mixing andconvective clouds reaching to theupper troposphere. The lowertropospheric mixing process is themain source of slow, westwardmoving pollution episodes thatproduce maxima in troposphericcarbon monoxide and ozone justsouth of the Equator, and extend tothe western tip of South America.Thunderstorm mixing of pollutantstends to lead to southeastwardmovement of these pollutants, andgreat pinwheeling plumes of carbonmonoxide and ozone spin out fromthe central convective areas of Africaand especially South America,particularly above 8 kilometers. Themodel has successfully simulatedaircraft observations in many details,and seems to explain more generallythe satellite observations of carbonmonoxide.

Most ozone in the modelsimulations seems to be made closeto the source, over the continent,only a day or so downwind of theagricultural burning that is its source.Theory and models suggest thatnitrogen oxides die out, and ozoneproduction must then cease. Obser-vation, however, has shown aremainder of chemically significantconcentrations of nitrogen oxides inthe middle and upper troposphere. Itis, therefore, suggested that there is a“re-NOx-ification” process thatreproduces photochemically activenitrogen oxides, NOx.

Point of Contact: R. Chatfield(650) [email protected]



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Instrument forTropospheric NitrogenStudiesJames R. Podolske

An open path tunable infraredmonitor of the atmosphere(OPTIMA) instrument is beingdeveloped to measure nitric acid(HNO3) and nitrogen dioxide (NO2)from the NASA DC-8 aircraft.Assessing the effect of the currentfleet of commercial subsonic aircrafton the Earth’s atmosphere requiresdetailed knowledge of the nitrogenchemistry of the upper troposphereand lower stratosphere. To date,understanding of this problem hasbeen hampered by large uncertain-ties, both in the abundances of theodd-nitrogen reservoir species and inthe partitioning of reactive nitrogen(NOy) between nitric oxide (NO)and NO2. Among the nitrogenreservoir species, HNO3 is expectedto be one of the predominantcompounds. Presently, numericalmodels of the upper trososphere andlower-stratosphere region predictNOx and NOy partitioning whichdiffers greatly from that derived fromexisting measurements. Currentinstrumentation has been shown tobe inadequate for measuring HNO3and NO2 with the speed and accu-racy required to advance under-standing in this area.

The OPTIMA instrument uses aninfrared laser spectrometer coupledto an actively aligned multiple passHerriott sampling cavity whose openabsorption path between the fuse-lage and the inner engine pylonachieves a free-stream absorptionpath length of 384 meters. To furtherenhance the detection sensitivity of

this tunable infrared diode lasersystem, high-frequency wavelengthmodulation spectroscopy isemployed. Detection sensitivity forthese two gases is expected to be inthe one-to-ten parts per trillion byvolume range. In FY96, tests of theaircraft wing dynamics required tospecify the alignment system werecompleted. The preliminary designof all the instrument subsystems wascompleted, and the final designreached the 50% level.

Point of Contact: J. Podolske(650) [email protected]

Reactive Nitrogen andOxygenated HydrocarbonMeasurements during thePacific ExploratoryMissionHanwant B. Singh, W. Viezee,R. Chatfield, Y. Chen, D. Herlth,R. Kolye

The Pacific troposphere is amajor region of the northern hemi-sphere that is relatively free of directinfluences from man-made pollu-tion. Tremendous industrial growthin Asia and North America in recentdecades has the potential to signifi-cantly affect this pristine region.The Pacific Exploratory Mission-B(PEM-B) and -Tropics (PEM-Tropics),performed in collaboration withL. Salas of the San Jose State Founda-tion, are major contributors to theNASA Global Troposphere Experi-ment, designed to study the state ofthe perturbed and the unperturbed

atmosphere over the Pacific Ocean.These experiments aim to elucidatemechanisms by which ozone in thetroposphere is formed, destroyed,and transported. To achieve this aim,data from the PEM-B mission wereextensively analyzed and a new setof field measurements involvingnitrogen, carbon, sulfur, and tracerspecies were performed during afive-week PEM-Tropics deployment.Major deployment sites for PEM-Tropics were California, Fiji, Tahiti,Easter Island, and New Zealand.Highly sensitive measurements ofreactive nitrogen species, oxygen-ated hydrocarbons, and chemicaltracers were performed by the Amesgroup by deploying an instrumentcalled PANAK (PANs/aldehydes/ketones).

Point of Contact: H. Singh(650) [email protected]

Subsonic Aircraft: Contrailand Cloud Effects SpecialStudyOwen B. Toon, Steve Hipskind,Duane Allen, Paul Bui, Roland Chan,Mike Craig, Guy Ferry, Steve Gaines,Warren Gore, Eric Jensen, Joe Jordan,Stefan Kinne, Bill McKie,Peter Pilewskie, Rudi Pueschel,Tony Strawa, Annette Walker

The subsonic aircraft: contrailand cloud effects special study(SUCCESS) program was a NASAfield program that used scientificallyinstrumented aircraft and ground-based measurements to investigatethe effects of subsonic aircraft on


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contrails, cirrus clouds, and atmo-spheric chemistry. SUCCESS hadseveral objectives. One was to betterdetermine the radiative properties ofcirrus clouds and contrails so thatsatellite observations can morereliably measure their effect onEarth’s radiation budget. Studyquestions included determininghow cirrus clouds form, whetherthe exhaust from subsonic aircraftpresently affects the formation ofcirrus clouds, and, if the exhaustdoes affect the clouds, whether thechanges induced are of climatologi-cal significance. Several newinstruments were also developed.The study also helped to betterdetermine the characteristics ofgaseous and particulate exhaustproducts from subsonic aircraft andtheir evolution in the region near theaircraft.

To achieve these experimentalobjectives, the NASA DC-8 and T-39aircraft were used in situ as samplingplatforms; the NASA ER-2 aircraftwas deployed as a remote-sensingplatform; and the NASA 757 wasused as a source aircraft for studiesof contrails and exhaust.

The experiment was cospon-sored by NASA’s Subsonic Assess-ment Program and the RadiationSciences Program, which are part ofthe overall Aeronautics and Missionto Planet Earth programs, respec-tively. SUCCESS had well over ahundred direct participants fromseveral NASA Centers, other govern-ment agencies, universities, andprivate research companies.

The SUCCESS project wasconducted from the Kansas StateUniversity airport facilities in Salina,Kansas, from April 8, 1996, untilMay 10, 1996, with an extension

from May 10 until May 15, 1996, atNASA’s Ames Research Center.SUCCESS coordinated with the U.S.Department of Energy’s (DOE’s)Atmospheric Radiation Measure-ments Program, which operates theCloud and Radiation Testbed (CART)site located in Northern Oklahoma.In addition to the extensive ground-based measurements at the CARTsite, DOE also operated an Egret anda Twin Otter aircraft, mostly usingremote-sensing instruments.

Point of Contact: S. Hipskind(650) [email protected]

Stratospheric Tracers ofAtmospheric TransportStephen Hipskind, Michael Craig

The primary goal of the Strato-spheric Tracers of AtmosphericTransport (STRAT) program is themeasurement of the morphology oflong-lived tracers and dynamicalquantities as functions of altitude,latitude, and season in order to helpdetermine rates for global-scaletransport and future distributions ofhigh-speed civil transport (HSCT)exhaust emitted into the lowerstratosphere. The observationsobtained will improve understandingof broader issues involving transportof gases and aerosols in thestratosphere.

A secondary goal of STRAT isthe further characterization ofatmospheric photochemistry. Asshown in earlier airborne cam-paigns, measurement of free radicalswithin the context of a sufficiently

large suite of tracer observationsprovides stringent tests for under-standing the processes that controlozone photochemistry. The STRATcampaign has extended the regionsand seasons for which such mea-surements have been taken.

The experiment made atmo-spheric observations with an arrayof instruments on the NASA ER-2aircraft that measured long- andshort-lived chemical tracers, meteo-rological parameters, radical species,aerosol particles, and solar radiation.The experiment consisted of six fieldcampaigns of approximately two tothree weeks each. The individualcampaigns consisted of local,midlatitude flights out of AmesResearch Center and tropical flightsto and from the island of Oahu,Hawaii. Included in the February1996 campaign was a coordinatedflight with the NASA DC-8 aircraftduring the Tropical Ozone TransportExperiment/Vortex Ozone TransportExperiment mission. In the coordi-nated flight, the ER-2 made measure-ments while flying in the exhaustplume of the NASA DC-8 aircraft.

STRAT was sponsored byNASA’s Atmospheric Effects ofAviation Project, Upper AtmosphereResearch Program, and AtmosphericChemistry Modeling and AnalysisProgram.

Approximately 100 participantsfrom Ames, other NASA centers,other government agencies, universi-ties, and private consulting compa-nies were involved in this research.The ER-2 carried a complement of15 scientific instruments, makingprimarily in situ measurements withtwo remote-sensing instruments.Overall, 53 flights of the ER-2 usedmore than 260 hours of flight time.



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STRAT has provided a richdataset with seasonal coverage overtwo years, vertical profiles from theupper troposphere to the lowerstratosphere (33,000 to 70,000 feet),and latitudinal coverage fromapproximately 2 degrees South tomore than 60 degrees North. Theanalysis of these data will increaseunderstanding of the transport anddistribution of emissions into thelower stratosphere by future HSCTs.The data from the first three deploy-ments has been published onCD-ROM.

Point of Contact: S. Hipskind(650) [email protected]

Tropospheric AerosolRadiative ForcingObservational ExperimentPhilip B. Russell, John M. Livingston,Wendy Whiting

The overall goal of the Tropo-spheric Aerosol Radiative ForcingObservational Experiment (TARFOX)is to reduce uncertainties in theeffects of aerosols on climate bydetermining the direct radiativeeffects, as well as the chemical,physical, and optical properties ofthe aerosols carried over the westernAtlantic Ocean from the UnitedStates. Other objectives of TARFOXare (1) to perform a variety of closurestudies by using overdetermineddatasets to test the mutual consis-tency of measurements and calcula-tions of a wide range of aerosolproperties and effects; and (2) to use

the results of the closure studies toassess and reduce uncertainties inestimates of aerosol radiativeforcing, as well as to guide futurefield programs on this subject.

An important component of theclosure studies is tests and improve-ments of algorithms that retrieveaerosol properties and effects fromsatellite and aircraft radiometers. Theresulting validated algorithms willpermit extensions of the TARFOXresults to other times and locationsthat have aerosol properties similarto those of the TARFOX IntensiveField Period (IFP).

NASA Ames contributed toTARFOX by supplying the ProjectScientist, Project Manager, anER-2 aircraft, and two airbornesunphotometers. The TARFOX IFP,including coordinated measurementsfrom four satellites (GOES-8, NOAA-14, ERS-2, LANDSAT), four aircraft(ER-2, C-130, C-131, and a modifiedCessna), land sites, and ships, wasconducted July 10–31, 1996. Avariety of aerosol conditions weresampled, ranging from relativelyclean behind frontal passages tomoderately polluted, with aerosoloptical depths exceeding 0.5 atmidvisible wavelengths. The latterconditions included separateincidents of enhancements causedprimarily by anthropogenic sourcesand another incident of enhance-ment apparently influenced byrecent fog processing. Spatialgradients of aerosol optical thicknesswere sampled to aid in isolatingaerosol effects from other radiativeeffects and to more tightly constrainclosure tests, including those ofsatellite retrievals.


The combined surface, air, andspace datasets obtained in TARFOXwill permit a wide variety of closureanalyses. “Internal closure” will beassessed by comparing the quantitiesthus derived with those deducedfrom the simultaneous in situmeasurements of aerosol sizedistribution and chemical composi-tion. “External column closure” willbe assessed by comparing aerosolextinction computed from the in situmeasurements on the C-131A withthose derived from the airbornesunphotometers, satellite radiom-eters, and ER-2 imagingspectrometers.

Such closure analyses will yieldcritically needed assessments andshould reduce the uncertainties inderived values of anthropogenicaerosol radiative forcing. The closureanalyses that use satellite opticaldepth and flux results will providetests and, where necessary, improve-ments of satellite retrieval algo-rithms. The resulting validatedalgorithms will permit extensions ofthe TARFOX results beyond theTARFOX period and to other loca-tions dominated by similar aerosols(for example, the European Atlanticcoast).

Point of Contact: P. Russell(650) [email protected]

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Atmospheric Physics

Fine Particle Emissionsby AircraftRudolf F. Pueschel, Guy V. Ferry,Anthony W. Strawa, Duane Allen

Collections of aerosols weremade with the Ames wire impactorsaboard the NASA DC-8 aircraftflying in the exhaust of a Boeing 757aircraft during the subsonic aircraft:contrail and cloud effects specialstudy mission. Morphologicalanalysis of scanning electronmicrograph (SEM) images andenergy-dispersive analysis of x-raysemitted during exposure of theparticles to electrons in the SEMallowed a distinction betweensulfuric acid (H2SO4) and sootaerosols. Size classification andintegration over size distributionsof both types of aerosols yieldedambient concentrations, particlesurface, particle volume, andparticle effective radii. This researchwas performed in collaboration withJindra Goodman of San Jose StateUniversity, Steve Howard ofSymtech, Sunita Verma of TMA/Norcal, and Glenn Sachse of theNASA Langley Research Center.

The ambient carbon dioxide(CO2) concentrations, determinedat NASA Langley Research Center,were 1.E-4 to 1.E-5 times theconcentrations emitted at the engineexhaust plane. Applying thesedilution factors to the soot andH2SO4 aerosols yielded emissionindices between 0.05 < EIH2SO4 <0.5 grams per kilogram of fuel and2.5E-4 < Eisoot < 1.4E-3 grams perkilogram of fuel, respectively.

Relating the H2SO4 emissionindices to the fuel-S (sulfur) contentresulted in the sulfur gas-to-H2SO4particle conversion of between9␣ and 24%. This result is close butoutside the range of 3 to 12% ofsulfur oxidation that could beattributed to hydroxyl radical (OH)-limited gas-to-particle conversion.Thus, a mechanism of H2SO4generation in aircraft exhaust thathas yet to be determined appears toexist.

The 1990 fuel use by thecommercial airline fleet amountedto 1.3E11 kilograms. If the fuel-Scontent averaged 500 parts permillion mass, a conversion efficiencyof 20% would have led to a contri-bution by aircraft of 1.3E7 kilogramsof H2SO4, or approximately one partin 1.E4 of anthropogenic sulfate ion(SO4) from other sources. If anaverage Eisoot = 7.5E-4 grams perkilograms of fuel is assumed, theannual emission of soot into theatmosphere in 1990 would haveamounted to 1.E5 kilograms. Com-pared with 24␣ teragrams of totalanthropogenic soot emission, itfollows that aircraft contributionswould have amounted to one part in1.E5 parts of total soot aerosol.

Thus, aircraft appear to be onlya minor source for both H2SO4 andsoot aerosol. Nevertheless, themeasurements reported highlight theissue of particulate (soot and sul-fates) emissions from aircraft. Thepotential for the aircraft emissions ofwater vapor (H2O), sulfur (S), andparticulates to change the nitrogenoxides (NOx) effectiveness toatmospheric ozone (O3) changes

may be sufficiently significant to beincluded in models.

Point of Contact: R. Pueschel(650) [email protected]

FIRE Phase IIIPeter Pilewskie, Warren Gore

Begun in 1986, the First Interna-tional Satellite Cloud ClimatologyProject Regional Experiment (FIRE)has been an ongoing multiagencyprogram designed to promote thedevelopment of improved cloud andradiation parameterizations for usein climate models, and to provide forassessment and improvement ofInternational Satellite Cloud Clima-tology Project products. The strategyof FIRE has been to combine model-ing activities with satellite, airborne,and surface observations.

The third phase of FIRE, or FIREIII, has begun with renewed efforts tounderstand the physical and dynami-cal properties of climatically impor-tant cloud systems, cirrus, andstratiform clouds. Project personnelcompleted the second year’s workdeveloping new solar spectralradiometric instrumentation forcloud remote sensing and atmo-spheric radiative flux measurements.In FY96, progress was made towardFIRE III goals by testing a prototypesolar spectral flux radiometer (SSFR)at a ground site during the NASAsubsonic aircraft: contrail and cloudeffects special study mission. Asidefrom providing important informa-tion on the solar radiative propertiesand effects of cirrus and cirrus

A T M O S P H E R I C P H Y S I C S

ATMOSPHERIC PHYSICS


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contrails, the benefit of the surfacedeployment was the expedition ofthe development of the airborneSSFR, which will be flown in 1997.The team will have airborne andsurface capabilities to determine thenet solar spectral flux at multiplelevels in the atmosphere, and cantherefore determine the spectralabsorption characteristics of theclear and cloudy atmosphere.Uncertainties in the amount of solarradiation absorbed by water vaporand clouds continue to be a majorfocus in atmospheric radiative andclimate studies.

Point of Contact: P. Pilewskie(650) [email protected]

Laboratory Spectroscopyof Carbon Dioxide inSupport of PlanetaryAtmospheres ResearchLawrence P. Giver,Charles Chackerian, Jr.

Spectra of planets have absorp-tion bands caused by the moleculesin their atmospheres. Measurementsof these spectral features can yieldinformation about these planetaryatmospheres, such as the abundanceof the absorbing molecules and thepressure and temperature of the gas.Measurement requires knowledge ofabsorption band absolute intensities,line positions, pressure broadeningparameters, and temperature depen-dencies. Over the past 30 years,measurements of these parametershave been made on absorption

bands that are relevant for planetaryspectra in the NASA-Ames HighResolution Spectroscopy Laboratory.

In collaboration with D. C.Benner of the College of Williamand Mary and NASA LangleyResearch Center, and L. R. Brownand J. S. Margolis of the NASA JetPropulsion Laboratory, recent workhas emphasized intensity measure-ments of very weak near-infraredcarbon dioxide (CO2) bands that areimportant for understanding thespectrum of the night side of Venus,which has a massive CO2 atmo-sphere. The first intensity measure-ments of several of these bands weremade using spectra obtained atAmes; an article reporting thesemeasurements of bands in the7000-per-centimeter region waspublished in the Journal of Molecu-lar Spectroscopy. Also, measure-ments of the perpendicular band at5315 per centimeter were reportedat the Seventh Annual Conferenceon Laboratory Research for PlanetaryAtmospheres in Kona, Hawaii, inOctober 1995. Collaborationbetween Ames and the NASALangley spectroscopy group resultedin a careful comparison of intensitymeasurements of the band at4006 per centimeter; these resultswere presented at the Fifty-first OhioState Symposium on MolecularSpectroscopy in June 1996.

As an extension of prior workon the visible spectrum of methane(CH4), which is abundant in theatmospheres of all the outer planets,two spectra obtained at the Kitt PeakObservatory have shown that apreviously unidentified absorptionline in Saturn’s spectrum at

6584.3 angstroms is a relativelyisolated methane line.

Point of Contact: L. Giver(650) [email protected]

Near-Infrared RemoteSensing of Cloud LiquidWaterPeter Pilewskie, Warren Gore

The 1995 Arizona Program wasa multiinvestigator field experimentaimed at advancing the understand-ing of winter storm development,morphology, and precipitation in amountainous region of centralArizona. From January 15 throughMarch 15, 1995, a wide range ofinstrumentation was in operationin and around the Verde Valleysouthwest of Flagstaff, Arizona,including the Ames visible and near-infrared spectroradiometers, twoDoppler radars, an instrumentedaircraft, a lidar, microwave radiom-eters, and other surface-basedinstrumentation focused on theanalysis of wintertime storms in thisgeographically diverse area. Over25␣ scientists from seven institutionstook part in the program.

Of special interest to the Ari-zona Program is the interaction oftopographically induced gravitywaves with the ambient upslopeflow. It is hypothesized that thesewaves may augment the upslope-forced precipitation that fallsdownwind of this feature onto theMogollon Rim. A major thrust ofthe program is to compare the


168

observations of these, and otheraspects of winter storms, with thosepredicted with a numerical model.

The primary role of this researcheffort was to provide cloud remote-sensing analysis for determiningcloud water thermodynamic phase,cloud thickness, and liquid watercontent (LWC). The unique collec-tion of surface and in situ sensorsprovided valuable data toward futureefforts in determining the relation-ships between cloud radiativeproperties and microphysics andinvestigations into the role of cloudsin climate. Understanding the role ofclouds in climate is predicated notonly on determination of the com-plex manner in which radiativeenergy is redistributed by clouds butalso on the hydrological processesthat regulate the distribution ofcondensed water and water vapor inthe atmosphere. There are funda-mental gaps in the present under-standing of the hydrological cyclethat limit the ability to assess thepresent climate, let alone predictfuture climate, or climate responsein the presence of increased green-house gases. Because the removalrate of condensed water dependsstrongly on cloud LWC, determiningthe distribution of LWC and itsdependence on temperature arecrucial toward a better understand-ing of cloud-climate feedback.

Analysis of the Arizona Programdata continued in FY96. A newmethod of analyzing surface-basecloud transmission spectra, devel-oped during the first year of thisproject, was useful in deriving bothcloud liquid water as well as watervapor. Presently, the retrievalmethod derives the relative propor-tions of those quantities. New

analysis, based on photon pathlength distribution calculations, willbe necessary to obtain liquid waterand water vapor in absolute units.Nevertheless, the work completedduring the two years of this projectwent far in developing this newremote-sensing technique, and willcontinue in the First InternationalSatellite Cloud Climatology ProjectRegional Experiment. Furthermore,the instrument developed for thisstudy, and the data acquired duringtwo major field campaigns, wereapplied to other current problems insolar radiative transfer, namely, theamount of radiation absorbed inclouds, and the amount of radiationabsorbed in the cloud-freeatmosphere.


Quantitative InfraredSpectroscopy of MinorConstituents of the Earth’sAtmosphereCharles Chackerian, Jr.,Lawrence P. Giver

The objectives of this study areto obtain quantitative laboratoryspectroscopic measurements ofmolecular constituents, which are ofimportance in understanding the“health” of the Earth’s atmosphere,and, in particular, emphasize thosespecies that are important forunderstanding stratospheric kineticsor are used for long-term monitoringof the stratosphere. These measure-ments provide: (1) line and band

intensity values needed to establishlimits of detectability for as-yet-unobserved species and quantify theabundance of those species that areobserved; (2) line positions, halfwidths, and pressure-induced shifts,which are all needed for remote andin situ sensing techniques; and(3)␣ data on the basic molecularparameters at temperatures andpressures appropriate to the realatmosphere.

Previously, oxygen (O2) pressurebroadened spectra of the nitric oxide(NO) vibration-rotation fundamentalwere obtained using a flow system.These are the first such data to berecorded. These spectra will beanalyzed for O2 broadening coeffi-cients for use in interpreting atmo-spheric retrievals of NO abundance.High-quality 0.005-per-centimeterresolution spectra of nitric acid(HNO3) were obtained in the1100- to 2700-per-centimeterspectral region. Rovibrational lineintensities on these spectra will bedetermined to support the OpenPath Trace Species Measurements inthe Atmosphere experiment. Analy-sis for the electric dipole momentfunction of the ground electronicstate of the hydroxyl radical (OH)molecule was completed using avery large set of relative emissionlines of the Meinel system. Adefinitive and comprehensivecompilation of rovibrational intensi-ties for the carbon monoxide (CO)molecule in its various isotopicforms was published.

An experimental feasibility studywas completed for using magneticrotation spectroscopy (MRS) todetect free radical molecular species(in situ) in the part-per-trillion mixingratio range. A quantitative theory



169

was developed to analyze the MRSresults obtained as well as to predictinstrumental parameters required forparts per trillion by volume detectionof free radical molecular species. Amultipass reflection cell inside asolenoid magnet has been con-structed to achieve parts-per-trillion-by-volume sensitivity.

Infrared spectra were obtainedusing an interferometer and a25-meter base-path multiple reflec-tion cell, in the 1.8-micrometerregion of the infrared red spectrumof nitric oxide for the purpose ofdesigning a lidar-based smoke-stackdetector for this molecule.

Experiments have been per-formed to measure line intensities ofgaseous water in the 1-micrometerspectral region to help in under-standing the apparent anomalyassociated with absorption of solarradiation by clouds in the Earth’satmosphere.

Collaborators in this researchinclude Chris Mahon of the SpacePhysics Research Institute,P. Varanasi of the State Universityof New York, and D. Cooper of theStanford Research Institute.

Point of Contact: C. Chackerian(650) [email protected]

Stratospheric TransportRudolf F. Pueschel, Guy V. Ferry,Anthony W. Strawa, Duane Allen

The atmospheric impact ofemissions by aircraft depends onhow they change the steady-stateabundance of constituents overbackground atmospheric amounts,

and on the role they play in atmo-spheric photochemical, dynamical,and radiative processes. Transportplays a role in this scheme, becausethe background concentrations ofatmospheric constituents vary inspace. For example, effects oncolumn ozone of aircraft-emittednitrogen oxides (NOx) result fromdecreases in the middle and upperstratosphere and increases in thelower stratosphere and troposphere.The balance between these increasesand decreases depends on thedispersion of the aircraft effluent byatmospheric transport processes, aswell as the transport of long-livedspecies, including ozone, in thebackground atmosphere. Thus, oneimportant aspect is that fraction ofexhaust NOx that would be trans-ported from the heavily traveledflight corridors in the lower strato-sphere in northern midlatitudes tothe tropics, where it can be lofted tohigher altitudes by atmosphericcirculation. Subsequent transportback to midlatitudes would be ataltitudes where the NOx from theexhaust dominates ozone depletion.

Of interest also is the fraction ofexhaust that could be transportedfrom the flight corridors in thenorthern hemisphere across theequator to southern latitudes.Transport of exhaust from north tosouth would reduce the concentra-tion of this fraction and mitigate theeffects in the northern hemisphere.

Soot aerosol measurements weretaken using the Ames wire impactorsamples to document barriers tointerhemispheric mixing, analogousto the stratospheric dispersion ofradioactive 14C tracers after thenuclear bomb tests in the 1950s andearly 1960s. Because atmospheric

nuclear bomb testing was terminatedin the early 1960s, the 14C datapermit estimates of interhemisphericmixing times that turn out to belonger than stratospheric residencetimes by more than one order ofmagnitude. This scenario explains adecade-long confinement of aircraftsoot to the hemisphere into which ithas been emitted.

Although there is agreementbetween the soot and 14C datasets inhorizontal interhemispheric mixing,vertical mixing between the sootaerosol emission level (12 kilome-ters) and the NASA ER-2 aircraftceiling (20 kilometers) is indicatedonly in the soot measurements.Transport from midlatitudes to thetropics, with subsequent lofting andtransport back to midlatitudes athigher altitudes, is a possibility forvertical mixing. However, since 14Cin the northern hemisphere does notsubstantiate the soot results, verticalmotion due to radiometric forces ofhigher absorbing soot particles thatcould prolong their stratosphericresidence times is a more plausibleexplanation.

This research was performed incollaboration with Jindra Goodmanof San Jose State University, SteveHoward of Symtech, and SunitaVerma of TMA/Norcal.

Point of Contact: R. Pueschel(650) [email protected]


170

SUCCESS IrradianceMeasurementsPeter Pilewskie, Warren Gore

A solar spectral flux radiometer(SSFR) was deployed at the U.S.Department of Energy SouthernGreat Plains Cloud and RadiationTestbed during April 1996 as part ofthe NASA subsonic aircraft: contrailand cloud effects special study(SUCCESS). The SSFR was used tomeasure downwelling solarspectral irradiance in the 250- to2500-nanometer solar spectralregion, with 10- to 15-nanometerresolution. From April 12 throughApril 29, approximately18,000 spectra were acquired,under a variety of meteorologicalconditions; a significant portion ofthe spectra was favorable to thestudy of cirrus clouds and cirruscontrails. Analysis of the solarspectral flux dataset will facilitatethe study of the effects of subsonicaircraft on the surface and loweratmosphere energy budget. Simulta-neous in situ observations by theNASA DC-8 will provide the micro-physical ground truth for assessmentof the results.

To determine radiative proper-ties of cirrus and cirrus contrails andtheir net effects on radiative energybudgets, a proper understanding ofthe solar radiation spectrum in thecloud-free atmosphere is needed.


A key component of the SUCCESSobjectives was to obtain a betterunderstanding of the spectraldistribution of solar irradiancereaching the surface. First resultsfrom analysis of SSFR data suggestthat absorption by water vapor canbe determined quite accurately, andthe measured spectra agree withmodel calculations within measure-ment uncertainties. These findingswill help eliminate long-standingdiscrepancies between theory andobservation and, likewise, arecrucial to determining the effects ofcontrails on the solar energy budget.


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The color plates in this appendix correspond to figure citations that appear in the text. Each caption also providesthe location of the figure citation.

Appendix

Color Plate 1. Air-traffic controllers at the Dallas/Fort Worth TRACON using FAST advisories to control arrivaltraffic. (Davis, p. 11)

A P P E N D I X

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Color Plate 2. F-15 ACTIVE superimposed on aerodynamic flight envelope. (Jorgensen, p. 19)

0

–1

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Color Plate 3. Full Apache AH-64D airframe aerodynamic loading in forward flight. (Duque, p. 36)

A P P E N D I X

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Color Plate 4. Vertical velocity contours and flow-field streamlines, 0-degree angle of incidence.(Stremel, p. 36)

Color Plate 5. Vertical velocity contours and flow-field streamlines, 15-degree angle of incidence.(Stremel, p. 36)

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Color Plate 6. Vortex cores (red) extracted from a simulation of a helicopter rotor in forward flight.(Kenwright, p. 39)

A P P E N D I X

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Color Plate 7. Interactive placement and visualization of streaklines in the Virtual Windtunnelpermits flow features to be easily found. (Kenwright, p. 42)

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Color Plate 8. PDV measurements of axial velocity and its root-mean-squarefluctuation amplitudes in a plane normal to the centerline of a low-speed, turbulentjet; the view in each image is upstream along the jet centerline. (McKenzie, p. 44)

A P P E N D I X

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Color Plate 9. The exVis ImageViewer window (left) shows pressure-sensitive paint data for theOAW-3 oblique all-wing model. The white line segments are slice tools that have been interactivelyplaced on the image. The GraphViewer (right) shows x-y plots of the coefficient of pressure versuslength along the tool for each selection. The highlighted peak (the red marker on the green graph)was selected in the GraphViewer, resulting in showing the black spot along the gray tool where thisvalue occurs. The third window (top right) is the simple user interface used to access datafiles andcreate ImageViewers and GraphViewers. (Uselton, p. 48)

Color Plate 10. Noise-level contours measured on 4.7%-scale DC-10 semi-span model in the Ames 12-FootPressure Wind Tunnel with 52-element Boeing phasedmicrophone array. (Horne, p. 56)

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Color Plate 11. Surface pressure contours for multiple design variable study: (a) original wing; (b)modified wing with four design variables; (c) modified wing with five design variables. (Greenman,p. 58)

Color Plate 12. Final mesh and computed pressure contours in the rotor plane. (Biswas, p. 59)

A P P E N D I X

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Color Plate 13. Four different types of grids used in computational fluid dynamics.Clockwise from upper left: multiple overlapping zone structured grid for the V-22 tiltrotoraircraft; periodic multizone structured grid for turbomachinery; hybrid structured andunstructured grid for a helicopter rotor; unstructured tetrahedral grid for the Langley fighter.(Bryson, p. 61)

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Color Plate 14. Optimized HSR configuration. (Cliff, p. 67)

A P P E N D I X

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Color Plate 15. Thin cirrus clouds scattered the light of the stars in this rare color photograph of the trail of analpha-Monocerotid passing the star Sirius, captured by the Dutch Meteor Society observer Robert Haas at theAlcudia-de-Guadix location in Spain during the meteor outburst of November 22, 1995. (Jenniskens, p.␣ 81)

184

Color Plate 16. An illustration of possible network of 24 PASCAL stations on Mars. This network is achievableusing centrifugal release from a spin-stabilized carrier spacecraft and two propulsive time-of-arrival adjustments.Three groups of eight stations each follow three sinusoidal loci and are marked by black circles (1st salvo), redsquares (2nd salvo), and blue diamonds (3rd salvo). Topography is shown in color contours. (Haberle, p. 88)

–60 –20 20 60 100 140 180–100–140–180

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Color Plate 17. The disk, showing apronounced annular gap at the halo/epicycle frequency resonance. Thispattern persists for the entire length ofthe experiment, which is on the orderof a Hubble time. (Smith, p.␣ 91)

Color Plate 18. Strong, non-axisymmetric structure is evident inthe disk at late times in theexperiment. This bar is absent whenthe halo remains static. Such offsetbars are often seen at the centers ofdisk galaxies. (Smith, p. 91)

Color Plate 19. (a) The SAGE II frequency of cloud occurrence from 0 to 100%in 5% increments. (b) The HIRS frequency of cloud occurrence from 0 to 30%in 1.5% increments. (c) The average tropopause height from 27,000 to 67,000feet in increments of 2,000 feet. (d) The MLS-derived water vapor overburdenfrom 4 to 24 precipitable microns in increments of 1 micron. (Haas, p. 95)

100 60140 120

2 4 6 8 10 12 16 18 20140

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Meteorological Data for the Summer (JJA) Season

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80 100 60 40140 120160180 80

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Color Plate 20. The image of the skull of the female from the Visible Human dataset is visualized on the screenof the Immersive WorkBench. Rei Cheng (left) and Muriel Ross are studying the 3-D reconstruction with the aidof special glasses. Rei Cheng is demonstrating special gloves that will be used to manipulate instruments andpieces of bone or other tissue in the immersive environment. (Ross, p. 119)

A P P E N D I X

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Color Plate 21. Global patterns of annual (a) N2O and (b) NO emissions from soils. (Potter, p. 149)

–90 60 30 0 30 60 90 120 150 180–120–150–180

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Color Plate 22. Top map: Conventional map of soil water holding capacity (SWHC)using homogeneous polygons. Bottom map: Map of SWHC developed in this research.(Coughlan, p. 152)

0

Scale: Kilometers

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A09

Research and Technology 1996

Ames Investigators

This report highlights the challenging work accomplished during fiscal year 1996 by Ames researchscientists, engineers, and technologists. It discusses research and technologies that enable the InformationAge, that expand the frontiers of knowledge for aeronautics and space, and that help to maintain U. S.leadership in aeronautics and space research and technology development. The accomplishments span therange of goals of NASA’s four Strategic Enterprises: Aeronautics and Space Transportation Technology,Space Science, Human Exploration and Development of Space, and Mission to Planet Earth.

The primary purpose of this report is to communicate knowledge—to inform our stakeholders, custom-ers, and partners, and the people of the United States about the scope and diversity of Ames’ mission, thenature of Ames’ research and technology activities, and the stimulating challenges ahead. The accomplish-ments cited illustrate the contributions that Ames is making to improve the quality of life for our citizens andthe economic position of the United States in the world marketplace.

Aeronautics, Space transportation, Space sciences, Earth sciences, Life sciences,Information technology, Research and technology

Technical Memorandum

Point of Contact: John T. Howe, Chief Scientist, Ames Research Center, MS 200-16, Moffett Field, CA 94035-1000(650) 604-5500 or contact person(s) at the end of each article

Documents

Research and Technology - NASA · Ames’ research and technology activities, and the stimulating challenges ahead. The accomplishments cited illustrate the contributions that Ames